Regarding smaller airfields - these are in uncontrolled airspace and there are a new set of different levels of radar service available. Generally we ask for "the best you have" which is a bit lazy but ATC seem to be understanding.
For a detailed explanation, go here:
http://www.takeflightaviation.co.uk/...edairspace.pdf
I have my own answers for your other questions but I suspect others will be able to give more accurate / definitive answers so I will leave that to them.
Regarding separate taps - to actually get hot water in the UK is a bonus, so don't complain if it comes out of a separate tap
