Thanks to all for your interest and generosity in responding. Notes in the body ext.
I read though everyones thoughts, and I think I see a general theme:
large format is king! (and I'm very tempted, but the cost of darkroom/camera set-up is just too much for me at present)
my assumptions about the format are more-or less correct, though 'improvement' over 35mm may not be as great as I expect.
My assumption about equipment requirements are not correct. There are a lot of recommendations for very low cost TLR's.
Most importantly I had one very insightful PM (I'm not sure if I should quote a PM, apologies if I get the etiquette wrong) effectively advising me to put more effort into improving my work with 35mm first. after thinking hard about my results and how I get them, I believe he's correct.
So, here's my plan:
stay with my 35mm for while & use my tripod more, much more,
take more shots with bracketing or simpy sacrifice a few shots on each roll to keep my 'projects' fresh in my mind for darkroom work.
buy a lightmeter to enable incident and improve/ease spot metering,
test my safelight and replace if necessary (I can hear a collective 'well; doh!'),
buy a better enlarger lens (unless someone can specificaly say that my 6-element 50mm Komura or 75mm Fujinon's are in fact, good enough? when I do well, my 8x10's seem deadly sharp to my inexperienced eye with the 50, though I admit to not having tried the 75 seriuosly yet)
use more Acros and less Tri-x, and try out that bottle of rodinal that came in one of my box-lots. If I like it better than D-76, buy some more! But generaly, move my 'standard' film/developer combo to smaller grain/higher accutance. And put more effort into keeping my chems fresh! (I can hear another collective 'well; doh!')
print more, lots more (hey, I like it! and as I'm thinking about what I'm doing I'm bound to improve, and using my chems quickly has to be better than dumping them due to age, right?)
Keep an eye out for bargain TLR, 'cause it's gonna happen sooner or later! Anything with a tessar taking lens and clean mirror methinks...)
Thanks again for all your support,
MattPC.