[andmikey]

> They make offers expecting that the vast majority of them will be met, rather than over-offering and expecting A-level results to prune the numbers significantly.

Notable exception to this would be Cambridge maths, who over-offer significantly for Mathematics (last year: 541 offers, 253 acceptances). Quite a lot of people miss their STEP offer so colleges can choose on results day who to take based on STEP, UMS, interview, etc. Though STEP unlike A-Levels was sat this year, so they're still able to do that selection.