@NicoAndTheNiners - I'm sorry you had such a negative experience of PBL. Your description of how it worked on your course is a very clear example of exactly how it is NOT supposed to be done. The whole point is that all students research all topics and discuss their findings, not that everyone in the group is dependent on one other student for all of their learning about one topic.
There are several medical schools that use PBL (Barts, Cardiff, Glasgow, Hull York, Keele, Lancaster, Manchester, Norwich, Plymouth, St George's, Sunderland, Warwick), although they use it in different ways and at different points in their courses.
St George's made a conscious decision to use clearing to pick up academically strong students who hadn't got offers elsewhere - a kind of back-door post-qualification application - rather than because they had any more difficulty than several other medical schools in filling their places. (I don't work at St George's, by the way.)
The most common reason for students to avoid a medical school is clinical placements' being too remote and isolating, which particularly affects schools in London. I don't think PBL is a major reason for prospective students to avoid St George's, as the first two years are mostly lecture-based with PBL a relatively minor component, although it becomes a bit more significant in the later years.
@HereIGoAgainAndAgain - Health Education England and the Medical Schools Council are particularly focusing on establishing contacts between medical schools and schools/colleges in areas that are currently "cold spots". They are running summer schools this year for this precise purpose. Also, medical schools themselves should be making efforts to reach schools that don't currently get any input.
I'd be wary of relying on shadowing experiences for anything other than seeing the inside of a clinical workplace. If he does shadowing in a hospital I'd say it's far more important to get to talk to the junior doctors (the more junior the better) and medical students on placement than to watch what the consultant does.