Effortless,
Just my opinion, but if you've had the Land Rover for 15 years and probably never changed the tap gasket, I'd have said that the piece of cork has done an excellent job. Just replace it with the genuine article from Blanchards and carry on with another 15 years trouble free motoring from the tap.
Nige
Edited: Just noticed, you have done it before. I'll go and stand in the naughty corner. However, I must admit, I've never had a problem with those gaskets.