Householder requiring to replace a rather old radiator valve.
Best description : probably 8mm inlet and outlet at bottom, side entry to radiator,
manufacturer Yorkshire Imperial, could be 20 years old.
Help with supplier?.
when you say 8mm inlet and outlet at bottom, do you mean double entry valves ? where both pipes go into one side of the radiator ?
If so, then you don't have to and it's best not to use the same valves. You will be able to fit any 8mm radiator valves to the radiator, one in place of the old valve and the other in place of the blanking plug / drain off at the other end.
All you will need to do is extend one of the pipes to the other end of the radiator and connect to the valve, it doesn't matter which pipe you extend.