If your buying new from a car supermarket consider the lack of warranty and no aftersales. The extended warranties they offer are often useless. I've heard a few horror stories with people buying imports with the extended warranties only saving a few hundred pounds. When they start having problems the warrantiy company doesn't want to know and the importer couldn't care less

If buying used avoid the C180 and C200, especially in the early 202 guise before the Kompressers, they're too under powered. IMO the best 202 was the C250 diesel.

May be of interest;
http://www.autotrader.co.uk/ - popular classifieds site
http://www.parkers.co.uk/choosing/carreviews/ - Car reviews