Hi Alan,
I know that my EPQ was certainly something that was valued in the application, and I think that might be what swayed it to an AAB, because I had to get an A in the EPQ. Of course, if you aren't doing an EPQ now then it is too late to start that, but I'm sure the application process will be different again now. Some Russell Group universities, UCL in particular have received a lot of negative press for the lack of state school students they take on, so one wonders if that will be part of the application process.
As for other things in the application, I think a good piece of advice is to not to put geography cliches in the personal statement e.g. I want to do geography because I like to travel/experience different culture. Just sounds like you are in it for the fieldtrips. Need to be something constructive - e.g. the relevance of the subject in real world issues, the possibilities of GIS, etc.
Also think about if you are interested in any of the broad areas the department is interested in. I'm not as sure about the human specialisations as I'm a physical geographer, but the key physical research done in the department is about Environmental Change (reconstructing from 1000s and millions of years ago, glacial and interglacial cycles), Wetlands and Fluvial (e.g. rivers, coasts), Ecology, and finally Climate modelling and Climate Change work. For human I know less, but I know historical geography is very strong, as is population migration - sorry if you are a human minded person.
Most of all, say something unique. A lot of people apply to UCL geog. Even better, I hope you go to private school.
I came from a state comprehensive and only know 3-4 people that were not privately educated.
All the best.