Is there any travel insurance that I can buy that would cover flying airplanes abroad?
Yes, but you need to specify what you want covered and up to what amount ?
* damage to the plane you rent while flying it yourself
* damage the plane causes to third parties while you fly it
* injury to the passengers while you fly it
* injury to yourself while you fly it
* injury to yourself while someone else flies it
* any limits and deductables you're willing to accept on your claim
* do you just want to cover medical expenses or do want lifetime disability pay too
etc,etc,etc...
As Backpacker said, some of these are covered by existing policies. Some of those come even with your credit card.
In my experience, UK insurers are a lot more expensive than continental European ones. But they get nervous once the stakes move beyond £250K. That is usually the upper limit of your cover.