I don't see the higher entry requirements of the London medical schools as a challenge, instead i think it makes the life of those straight A scorers easier. Those that still require AAB will definitely be oversubscribed this year, as many students don't necessarily have predicted grades of AAA. So, if you're a constant AAA scorer, go for those in London as they might receive fewer applications(in my opinion). My reasoning is based on the fact that many medical students gained entry without having AAA, in fact, a significant number of them achieved only AAB in the real exam. That means AAA doesn't automatically guarantee you an offer. People with AAB predicted grades wouldn't really bother to apply to those that require AAA(obviously), therefore applying to those medical schools would mean less competition among the applicants(but all of them will be having AAA).