Bongo Fury

I've seen a couple under £300...but TBH I know sod all about cars so don't know what is good and what is not.

Any suggestions as to what I should look out for and where I should look for it? I'm almost definitely going to have to sell my beloved bongo once fixed so I'm looking to do it as cheaply as possible.

Muchos Gracias.

To be honest, even if you'll be selling it after the repair, the cheap Chinese cylinder heads and head gaskets have caused lots of problems and failed to work properly. You won't be able to sell it at all, if it's still overheating .
You haven't included your location in your profile, so we won't be able to recommend any local, reputable repair places for you, but it will almost certainly pay you to use one.
I've moved this to the Techie section, as you'll get more replies there.