You could try the official Class Association policy, arranged with Craftinsure.
I at least have been very well served by them, and not only for my successive GP14s but for my trailer-sailer yacht as well. They are certainly my insurer of choice, and that is as a result of a business relationship built up over somewhere around ten years.
They understand the risks, and they understand sailing, helped in large measure by the fact that their senior Underwriter is a sailing man himself. So if you are reasonable and responsible and seamanlike, they well understand – and accept – the things that can occasionally go wrong if you slip up, or if someone else does so.
I have found them excellent when I have wanted extensions to my policies, for cruising. And their claims settlement is first class. We all hope never to have a claim, but it does occasionally happen. Over the course of ten years, with up to three boats simultaneously, I have had two theft claims (the last one being when my car was stolen, with a load of kit from the yacht inside) and one for a bent mast when several boats in our boat park blew over during an exceptional storm. In all three cases their settlement was prompt and courteous and efficient; and where I thought there were possibly slightly grey areas they were very concerned to ensure that I was fully recompensed.
They may not be the cheapest, but they are certainly good.