Loads on this GL, do a search, I found Porthcawl to be the cheapest and be very friendly, I also used Marden for a few years, although I have never had to claim! If you have your RYA Powerboat 2 there should be some leeway (sorry
) on the price.
You will want a wheel clamp, hitch lock and an engine lock, these are usually specified by the insurer, and if you want to tow toys check your covered, similarly leaving the boat on the water overnight I had to inform the insurance company.
Couple of good Ribnet features here:
Jk has done a good guide to RIB ins. here: The JK guide to insuring your pride and joy!
Similarly, Noble marine have done a feature:
Noble Marine, preventing theft guide.
Do post some pics when you take delivery