At £500+ it's not a realistic prospect I'm afraid. Maybe if there more affordable ones that becomes available then I definitely would want to take a look in-depth.
https://hackerboards.com/boards/nezha/
Not sure how easy they are to get ... but $99 is a great price.
These are very slow with limited RAM. It's possible to run Linux but it won't be much fun.
The bigger problem with the board above is the single core.