Sorry to hear about all your probs but as others have said it has happened to all us Bis owners. When I first bought mine I drove it from central London to the midlands and it started to overheat, mind you it got me all the way home, 120miles, and as I pulled on the drive the rad cap blew off and water went everwhere!
Turned out the fan had stopped working and on closer inspection one of the head studs was snapped so the head wasn't sealing properly. However, now it runs like a dream, so if you rebuild you will know what condition it is in and you can keep on top of it and in the end everything will be OK. Also you can get a thermostat kit from Ricambio that moves it from under the engine to on top of the head but it is expensive. Have fun!
PS you bought the best Bis colour but them I am bias!
STUEY - how are those Burners!