If you take two bikes with identical geometry, but one is hi-tensile gas pipe and the other is, say Reynolds 501 or 531, you will find very very little difference in perceived ride quality. I have lugged & brazed Raleigh Pioneers in 23 1/2" size, one made with 18-23 Hi-tensile the other with 501, so I can compare the exact same designs back to back. Both ride nice, the 501 is marginally lighter so could possibly be perceived as more "lively", but in pure comfort terms I don't think there is anything much in it. Your Townsend might be worth more used if it had a "quality" lightweight frame, but I doubt it would feel much different in the saddle.
I haven't encountered much in the way of component compatibility issues. All mine apart from my 3-speed are square taper BB axles, and I have been happily mixing and matching cranksets from donor MTB's and hybrids between bikes. So long as the axle is long enough for the inner sprocket not to foul the chainstay, I have been able to fit pretty much which bits I wanted. Generally I have found a like-for-like swap to be fine; if a triple came off, a different triple will go on instead.
The only mismatch I had was finding out a 40/48 double wouldn't fit where a 28/38/48 triple came off as it needed a longer axle so the 40T didn't touch the frame.
