Are we really comparing an S4 to a 1L Festa?!
Broadly speaking though I tend to agree, we need to figure out first of all exactly what the car will be used for and the must haves & must not haves. If we can get that sorted, then we can start offering proper advice: Anything before that point would be doing Craig a disservice.
Looking specifically at that car, it'll certainly make some lovely noises and feel half decent in a straight line, however it'll feel incredibly dull and understeery in the corners. Not a problem as it wasn't designed to handle corners well, just worth bearing in mind as you mention 'fun'. Also 120k miles could be asking for big bills, as things start to fail. Okay, it's cheap enough so it's a fair sale, but you'd want a good £2K slush fund to fix and repair anything I think.