I agree with the comments above. Kruegers at New Milton are very good indeed. I have just bought a D4 from them (after talking about it for four years.....) and it looks so simple that I thought I might install it myself to save a few bob. If you go down that route I know a few chaps that would give you a hand in order to earn a pound or two after Christmas. Drop me an email if you want them.
Thanks for the responses. Kreugers are sounding favourite - any difference between the New Milton and Portsmouth branches? Any idea what would be a typical install cost given that the boat came with all the bulkheads/uprights already cut for heating?