I am in the UK and need to replace some coving, and am not sure how to track it down. It's probably 20 years old now, but I'm not sure if it's a generic size?
Looks like pretty generic coving to me.
If you're not sure if it's a generic size... then find out! Easiest way to check that is to walk into your local DIY store (B&Q, Wickes, whatever) with that small bit and check to see if they stock something similar.
Turns out (after pulling.it all down) it is Gyproc, readily available from selco