Well guys, thanks for the many responses. Looks like some of you have been at this issue before! Never occurred to me that the flange may have gotten out of shape, I'll check that and also try a sealent.
The pipe doesn't appear to be cracked, the leak is stemming from the front of the seal.Looks like an aftermarket replacement will be good, but being in the UK means waiting for parts so i'll try the various suggestions first.