Connecting British telephone sets to Astribank (or any other PSTN, PBX or
FXS line). It seems to work well. e.g: gives dialtone, dials, talks are heard. Only one thing is wrong: you don't hear any ring. What is wrong here?

This is because British phone sockets are non-standards, and hence British phones have to be connected trough as traditional master phone socket. To undestand the problm and how to fix it, see:

http://www.tkk.fi/Misc/Electronics/circuits/uk_wiring.html