Yachtmasters in Woodbridge (as Roach Says), they are very good, I used to use them, until I bought a boat which the previous insurers were happy to continuing covering without a new survey. Wehring Und Wolfes in Germany. I can PM you if interested.
50 foot Fife? Lots more details please! Are you going to keep it on the East Coast? Will you come to the Suffolk Yacht Harbour Regatta? I for one would love to see it there.