Erik Loye

Buying any old car you have to be careful, check or have a specialist check every mechanical and body part of the car. Buy the best (you can afford).
On maintenance I agree with Jonathan.
3 years ago I bought to mentioned rules a Spider 1970 (similar in all respect except for being soft top) that had been reconditioned some year and 5000 km earlier, knew I would have to deal with some issues with sills and some electrical.
The sills (and lower pars of the wings) was complicated (and expensive), electrical fairly straith forward. Other than that and a good service before starting to use it, it has behaved well and been very reliable, use it very often except during winter, done about 20000 km since.
I used to own MGBs and other MG models when they were new, Alfas of the same age are much more sophisticated, faster, better road holding and more comfortable than most British sports cars.
Erik