Hi Iain, ther are a few ways of going about this to be honest. If you are looking to insure the item to the total value you have stated, it will cost a fair bit. Usually the standard insurance cover on Parcelforce global express or priority is £500. After that, you have to pay extra to get the insurance up.
Needless to say, you must go for a fully trackable service from door to door and you need to check this. Some international services only track the item in detail until it leaves the UK which will not give you the piece of mind you need.
I would say generally Global Express should be good enough. You will need to state the items worth and fill out the usual customs info. If the piece is insured as standard to £500 then this will be all you can claim in the eventuality that it gets lost/ damaged. Depending on the nature of the piece and the current condition it might be worth paying for the extra insurance. For example, if I was shipping a yellow bubbled high end POTF figure it might be worth it as they can sometimes burst through bubbles in transit.
I have used global express to ship several 3 packs now and never had an issue. Sometimes the buyer has asked me to insure it fully at their cost and sometimes they have been happy to go with £500 cover and take the risk. Check with the buyer first as Im sure you will. Whatever you do, keep hold of the receipt and check the tracking regualrly for updates. It should be there in a week.
Good luck, Chris.