Preferably Shimano but would consider others.
Going to be using an 8-speed cassette and chain with friction shifters so 8/9/10 speed stuff should work okay.
V-Brakes - just the brakes, no levers needed.
Chainset - double or triple with a reasonably big ring (40t+).
Front Derailleur - Bottom pull, 28.6mm or braze-on.
Rear Derailleur - Ideal would be a short or medium cage, but long would suffice (and give me a bit of flexibility I guess)
Wheelset - need a braking surface and preferably a rim wider than 19mm.
On a bit of a budget so Deore level is about right, not bothered about aesthetics provided they've got life left.