Thanks to everyone who contributed I called one of the above and they were very helpfull, he said that he rebuilds the fuel heater/cooler as very expensive to replace but mine wasn't leaking at all when warm. Only when cold and lost about 1in in expansion tank I made it home safely and checked water this morning and only lost a small drop again whilst first starting it. Will take the offending item off tomorrow and strip and clean it and refit. Will let you know how I get on
 

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