If you are reading this, this means that you want to know if this university is a good fit for you. Know that diversity at UCL isn’t stopping at simple ethnic multiculturalism, but also expanding to the diversity of thoughts and interests, all bright minds gathered at the same place (actually there are still some dumbass, but this is characteristic to our planet, you will find them everywhere). What I mean is that it is up to you to find the ones that are alike to you, the ones that will stimulate you, the ones you want to share your life with.
Academically, again, UCL is promoting diversity. Multidisciplinarity is part and parcel of all degrees. Indeed, even if you are taking a single honours degree, you will be able to take electives from a totally different field from what you are studying.
I would say that when applying to UCL, you need to bear in mind the power in your hands that you have. And this institution will unlock this potential that you have at its utmost, if you wish to and realise it.