Having spent a year at UCL, I must say it is a world-class university, with a great academic staff, and a vibrant, multi-national student community. One has the opportunity to engage with world-leading researchers in their respective fields, and one will be pushed to excel over the course of ones studies. Due to the large student body, one has to adopt a certain level of self-discipline, as one will in no way be nannied through ones degree. In my experience, one will get far if one takes the responsibility to seize the opportunities that are provided.
The University is situated in central London, which provides plenty of opportunities for socializing and experiencing various museums and cultural events. The Student organisation hosts several bars, where one may always pop by for a cold pint and nice co-students.
I would recommend UCL to anyone seeking an ambitious academic life and who feels ready to tackle the challenges one meets.