Your tip for using the same film stock is good though, as a novice you dont tend to think about things like that until you get yourself in a mess
I do the same fo black and white although I always get tempted to try cheap film out
Theoretically, film brand and type shouldn't make a lot of difference, or so I've read from knowledgeable sources (e.g., PE here on APUG). My experience is that color balance does vary a lot from roll to roll, though, particularly when comparing rolls processed at different labs or in different chemicals. I haven't done any systematic studies to see what makes the most difference, but logic dictates that if you eliminate as many variables as possible, you're likely to get the smallest difference in end results.
Does anyone have advice for assembling my own kit from separate chemicals rather than buying them ready matched? I have been given a quantity of BLIX from old kits which didnt have a stabaliser, but Im not sure what dev to match it with?
First, I recommend against using blix with C-41 films; use separate bleach and fixer instead. I've tried two different blixes (a mix-it-yourself formula and Paterson blix), and both produced noticeably grainier negatives with more washed-out colors than I get when I use separate bleach and fixer. That said, some other people are satisfied with blixes, so you should of course judge for yourself, but at the very least you might want to try a side-by-side comparison.
Second, AFAIK the brand or type of developer you use doesn't interact with the brand or type of blix or bleach/fixer that you use. Just follow the directions for each step. It's quite possible that I don't know of some important interaction, though, so if PE or some other more knowledgeable person contradicts me, take that advice instead of mine. FWIW, I've been using Kodak's standard (non-RA) bleach and fixer for C-41 for a while now, originally with Paterson's C-41 but now with a mix-it-yourself formula since Paterson stopped making their C-41 chemistry.