hi, i have bought my mini about a month ago, it's a facelift model with 54k on the clock...
two previous owners "LADIES" so car looks mint but wasn't maintained the way it should be.
Oil is 7000 miles over, supercharger belt never been changed etc...
car is going to the garage next week :-) and will get a full service, new spark plugs new superchager belt, oil, supercharger oil(bp 2380) filters. Top engine mount is leaking oil so it will be changed as well. there is some noise like worn bearing from supercharger belt area. I have bought one of these wheel bearings that are on belt tensioners to get it replaced in case that's the tensioner wheel...
rear brake pads need replacing.
Today i have noticed for the first time like a vibrating noise from like under the windscreen area rev or clutching didn't stopped it. stopped the engine and started again and it's gone...

Is there anything else i should the mechanic to check while he has it in bits?

I would just get the things done that you have planned and see how she goes.

could be the engine mount that's giving the vibration ?

Iain