belmama My experience was UG. DS did both his UG and Masters at LSE. In the same way that I was the only British student on my course, he was the only Brit out of 39 on his Masters. I think his UG was about a third British, but it tends not to matter in that quite a lot of the UK students will be first generation or from ethnic minorities. (If you have grown up in the only Chinese family in a town in the Welsh valleys, like one of DS' friends, somewhere like the LSE offers something quite different.) Equally there were overseas students who had been to school in the UK, and quite a large number who had grown up in third countries and gone to international schools.
It is a real advantage to be very interested in your subject as this then gives you common ground with your peers, whatever their background.
Neither I nor DS had any problems socialising. There is a lot going on on campus. DS was considerably more sober than me, and SU societies, rather than clubbing, suited him. In contrast I went to a gig almost every night and helped run Ents.
DD spent her lockdown year on an engineering intercalation at Imperial. She did not have a single British teacher but all were leaders in their fields. She was with a group of European students for her major group project which was a really good experience. Different disciplines (she was a medic, they were engineering Masters students), different nationalities, lots of Zoom and other practical problems like trying to order components from China during Chinese New Year. A Ukrainian friend who works for a small but very international IT firm described as the perfect introduction to real world experience. Time zones, cultural differences, different technical expertise and the need to deliver to a common aim. Even though there was no face to face, DD made some good friends through sport that she is still in touch with, the closest of whom is again not British.
But then DC grew up in Central London and they were used to friends who came from all over. If anything DD found the lack of diversity in Bristol disappointing. Others might find both London itself and the mix of students overwhelming. It is something to think about before applying.