Ours go entirely on GCSE grade for AS, and then based on AS and GCSEs for A2, but they also talk to you about what you expect to achieve and take that into account (so if you're predicted a C from your AS results but you say you're going to put the work in to get to a B, they'll see how you go initially and might up it if they think you're doing well enough. But if you're saying you can get from a D to an A, they'll take it less seriously)
None of the ones I've talked to mentioned a technical system other than that, but the GCSE thing at AS can be really annoying because it takes all your GCSEs into account not just the relevant ones for your subjects.