Hi and welcome to APUG!
To answer your question, there are all kinds of reasons why people choose to shoot on film and print in darkrooms. "Megapixels" is really not one of them. It's in al likelihood true that you get more resolution from a modern digital sensor than from a frame of 35mm film (though you'd still pay a lot to be able to exceed the information content of a sheet of large format film). And that matters ... if you're printing murals. The difference in resolution is indistinguishable to the eye for the most common print sizes. (Also, there are huge false equivalencies made because of the spatial arrangement of silver grains or dye clouds in an emulsion, and the way the eye sees their 'resolution' is very, very different from that in a grid of pixels, but that's another whole can of worms to discuss and only slightly relevant to your question. Just to say that as a result of the nature of the materials, film and digital sensors can sometimes bring a different 'look' to an image)
So let's get away from the question of which medium is better or worse -- particularly using resolution as measured in a unit that only applies to one of the media anyway. It's not a very helpful metric for any practical purpose.
So why shoot a medium that is expensive and time-consuming? Here are a few reasons that I have
no doubt others will add to or disagree with:
1.
It's expensive and time-consuming. By which I mean, once you've paid for your camera and your computer and your printer, shooting a digital image costs almost nothing (actually it costs a little bit of wear and tear on your shutter, bit it
feels free until you suddenly have the repair bill

). Shooting film means constantly buying film and paper to print it on (of course lots of people scan film too). It means having 36 frames on a 135 roll, or a dozen frames on a 120 roll. Or two frames in a 4x5 film holder. You stop 'spray and pray' photography. You bring a new awareness and mindfulness to each shot. You actually
look at each scene and image you make, because you are investing in each and every photograph. Of course you still screw up. Often. And a 35mm frame is still very cheap. But many, many of us find that the constraints of the medium make us better photographers.
2.
It's really cheap. What? I thought you just said it was expensive and time-consuming? See the first sentence above: "once you've paid for your camera and your computer and your printer". These are expensive items. And they go obsolete in about 15 minutes. I do have a couple of digital cameras that I enjoy using, and a decent computer that I bought because I need it for other purposes. But those were expensive items. And I still don't have a photo printer, because the ones I consider worth buying I can't afford. On the other hand I have a couple of really, really top-notch film cameras -- arguably some of the best cameras ever made -- that I bought for a fraction of the cost of my decent-but-far-from-the-best digital cameras. From a use point of view, a 10, 20, 30 or 40 year old film camera is much more valuable than a comparably aged digital. Digital means buying equipment ... again, and again, and again. And my first DSLR I couldn't wait to get rid of because it wouldn't do
basic things that I used to be able to do on my old Olympus OM-1 (like mirror lock-up). Oh yes -- and every time you get a newer, higher-resolution sensor, you'll find that your fast computer and big hard drive are suddenly slow and small again. By contrast, my enlarger projects fine-grained Portra just as well as relatively-course-grained HP5.
3.
All modern films are amazing. Kodak, Ilford and Fuji, along with some of the smaller manufacturers like Foma and Maco/Rollei have invested incredible time, energy and money into producing materials that render tone and colour in truly beautiful ways. It's not, of course, that you can't do these things in Photoshop (another annual expense btw) but that most people just don't have the time and energy to spend figuring out how to render a tone curve
just so. Instead most users just push the saturation and sharpening sliders until they destroy the integrity of their image. The speed advantage of digital is at least to a large extent offset by the time it takes to really master Photoshop to achieve what, to a large extent, is already built into modern films and papers. (I'm just learning colour printing at the moment, and I used to worry at the lack of control offered by colour papers. And instead I'm just blown away at the job they do 'out the box').
4.
The images will still be there in 30 years. I want to look up a document I wrote once at university. Here, have a look for a XYwrite file on this 5.25" floppy disk... Computers fail. Formats change. Those backups you carefully took get misplaced -- or the restore software doesn't exist any more -- or the disk format changes, or the CDs you wrote on have delaminated with age, or your new computer no longer has a SCSI / Firewire / USB-A connector. For all the promise of perfect, reliable copies, digital technology has been a terrible, terrible disappointment when it comes to durability. By contrast, pick up a book that was published 150 years ago. It might smell a bit musty, have a bit of mould growing on it; the pages might be yellowed but it is still as clearly readable as the day it was printed. Likewise, negatives are really durable and if processed and stored with even marginal care, remain printable for a very, very long time. Now imagine if Van Gogh or Monet had worked in digital media. We would almost certainly never have been enriched by their paintings. Okay, maybe I am not the next Van Gogh, but perhaps that judgement should really be left for others, no?
5.
It's a refuge. We experience a daily barrage of networked information. I used to spend 8 hours a day at work and a couple more at home sitting at a computer making software, and more recently analyzing data and reading & writing papers. Is this how I want to spend my hobby time? For me, no. Again for me, the process of slowing down,
looking with care at the world we are in, and carefully trying to capture some aspect of it in a physical artifact that I can touch, feel, smell, is a break from that constant assault of the 24 hour news cycle, the pressures and distortions of social media, the constant sense of urgency that the world throws at us. It is a peaceful and mindful experience producing beautiful (hopefully) objects.
5.
It makes us happy. This is arguably the most important. Nobody can tell you what medium is right for you. Don't believe anyone who tells you that you
ought to be shooting this or that way. For every reason I have given above about why to shoot film, there are other reasons to shoot digital. It is your time, money and energy you are investing, and you should invest it in the medium that makes you happier. For me nothing touches the exciting sense of possibility when I load film into a camera; the sense of paying attention when composing an image I'm investing in; the sense of almost-miraculous wonder as funny-smelling chemicals and arcane rituals of temperature and time-keeping turn the latent image into a negative, and the sheer satisfaction of watching an image develop on a piece of paper in a tray of developer. If you are more satisfied by fulfilling your vision through the technological marvel that is silicon sensors, modern software, and the undisputed excellence of modern inkjet printers, then that is what you should do.
Oh - you also asked about places to buy and process film. I see you're in the UK where you're blessed with a lot of options. I've had really good experienced dealing with the people at AG Photographic, and I order a lot of my materials from them even though I'm across the water in The Netherlands. But there are lots of other options.
Have a happy Sunday!