If you have a look in the gallery section at the small car sunday pics, there was a turbo mini there. Maybe one of the guys that went could fill you in on what it was.
You could probably pick up a CT12 (from a 1G-GTE) or a CT12A (From a 1JZ-GTE) pretty cheap from a Jap importer. That would be a good starting point for you.
I think I have a pic at home of a turbo Moke engine bay and I have heard that there was even some factory turbo mini's made, however I havn't seen one. It could be a myth.