Is it leaking along the pipe length or from the heater bulk head speed fit union ?
Reason I ask is I know the actual pipe has an internal diameter of 15mm.(..long story but a piece of copper pipe and 2 jubilee clips says it all..) so if its just the pipe you could cut and join it...just a thought ...failing that Im sure somebody will be breaking 1 if you ask admin to put up a "Wanted"
Yes, this is a good idea. I will do this if no success sourcing a new part. The leak is near the end without the connector so it should be possible so long as the old connector still functions without leaking after being removed and re-fitted.