Mine are all covered on the household goods insurance through Marks and Spencers.
They cover all items "unlisted", meaning you don't have to tell them what you have, for up to £4000 per item.
I have the Premium insurance which means they are covered worldwide, I believe this includes racing!
If you get a quote from them, tell them that I recommended them to you, and I'll get a £10 M&S voucher which will let me buy some new boxer shorts - some people may think this is important