As far as wheels and exhaust, most people in Aus get locally manufactured stuff, so what we suggest might be hard to come by.
I have seen a couple of early celica's with 15x7in minilites on them. They look really nice and have a fair amount of dish in them. You seem to have a much better range of minilites in the UK than we get here, I'de go for a big set of chrome/polished minilites.
As far as exhaust goes, I am not really sure what is available for you, You would have early corollas there, so I assume there is something available. Go for some good extractors/headers and a free flowing 2-2.5in pipe.