Lot's of people have done turbos on the 1275 midget using the MG Metro setup. And our own GlenB has done a homemade turbo set up for his Bugeye.
I have not seen a turbo on 1500 though. I think your biggest challenge on turboing a 1500 will be making the bottom end strong enough. 1500s have a notoriously weak bottom... and performance upgrades are not as readily available as they are for the 1275.
I have been fantasizing about a turbo for my own 1500. But that project is way, way, WAY down †he list for me.