The bane of all restorations: rust on the body work. My little one doesn't have too much rust but its none the less expensive to fix.
Biggest issue with my mini is the front end area is twisted, the bonnet catch doesn't match up anymore. Replacement front end has been received to replace that area.
Other then that, little bit of rust at the bottom of the doors, around the sills (who though a little shelf that lives to gather water was a good idea Mini designers?), some surface rust on the floor.