I second what Mike said, Blakey is good but VERY busy. I have an alternative if Mike's man is too busy. His name is Simon an his number is 01494 713087 Both parties will charge a fraction of what D.B. Marine charge.
I've used MMS at Marlow on the Harleyford Estate 01628 471368 ask for the manager Jason Brasier. They did my complete refit from petrol to diesel, exceeded my expectations by miles and they were high to start with - I'm fussy.
I'd also see if there are some mobile guys they might be cheaper.
Avoid RYB in Widsor - I had nothing but trouble out of them - personal opinion in case they read this - so you can't sue me boys.