My Father and I restored a 1979 MGB roadster in the late 90's, and from my experience, let me tell you a few things.
1. Look for rust, and look HARD. These things are prone to rust, and while it may appear that ther is only minor rust, the damage could be major. We had to totally redo the rocker panels, as well as the floorboards and lower fenders. Extensive bodywork.
2. Remember the dependability of the old MG's. To say they are not the most dependable vehicle on the road would be quite the understatement.
That being said, the MG is a blast to drive.
I have a '04 Corvette, and would you believe it, I get more looks in our '79 MGB than my '04 Vette -- and I get plenty of looks in the Vette.
Best of luck.