Hi Mark
I guess you are in the UK looking at that Mini.
What info have you already had from the present owner? If it is going at a good price, then worth a punt. You can always break and sell on Ebay.
Go and have a good look, record engine number, frame number and registration, you can then do a cheap check on the history. You can also have a better poke around and see what needs doing as well as find out how long its been standing
Cheers
Seamus