Don't go too wide with the tyres, granted yours has the slower non-PAS rack, but I had great fun in one of a similar age, they are so chuckable on roundabouts, can be really lairy without going fast; if you stick wide tyres on it (185 or more probably) then you loose that fun. You would have to go faster to get to the limit and the car won't go that much faster.
More importantly when you overcook it chances are you will be able to stop, rather than exiting the roundabout backwards...
IMO, Mk3 XR2i 13" alloys & front brakes would be a big win. 165/65R13's, or if you must, 185/60's.
Might be worth looking at how awful a job it would be to fit the quicker rack?
How about looking out for some body coloured bumpers maybe from a silver one? Don't forget the painted bumpers are different, they have more pronounced arches.