There are two potential insurers. Common advice is to ensure you have public liability insurance. This will protect against 3rd party losses, should you have some sort of failure which, results in damage. BMFA cover up to £25M for £32.00 per year. This includes membership of BMFA. The insurance policy will NOT protect against damage incurred in flight. It will protect you against loss due to theft or accident whilst in storage or transportation, but equally, your household contents insurance MAY cover you too.
The alternative for 3rd party liability cover is FPVUK which has similar 3rd party liability cover to the value of £5M for approx. £15.00 per year.
Protectyourbubble.com will NOT insure a quadcopter for accidental damage during flight. I didn't progress any further with them after talking with them on the phone.
Gadget-cover.com say they will protect against breakdown. Their policy is around about £100 per year with a £50.00 excess. I specifically asked whether they would insure against a replacement which broke down during flight (engine failure etc). The agent (note, NOT the actual insurer) stated that he thought the P2V would be covered as it suffered a breakdown during normal usage. The analogy he used was that it was similar to a mobile phone breaking down during a call. And whilst this would seem logical, one would have to get specific guidance from the actual insurer whether this indeed would be the case.
That said, if you read the sample policy there is a specific clause which falls within the items NOT covered, mentioning "12. Any loss or damage caused by the failure of any electrical or computer equipment, software, micro-controller, microchip, accessories or associated equipment to correctly recognise and process any calendar date or time."
Again, a lot of this is down to interpretation and wiggle-room on behalf of the insurer. Ultimately, as it's been stated elsewhere. You pays your money and you takes your chance. The 3rd party liability insurance is a no-brainer. It then falls to whether you want to risk £100 and fight the battle if something happens. As with everything, make sure you keep your receipts and that you FULLY read and understand the insurance policy. If you don't understand something, ask them for clarification.
hope this helps
Bmews