It is very common in London. I'm fortunate enough to be able to afford a place on my own, but almost all professionals seem to be living with someone else - either a partner or with roommates. I actually am thinking of switching to a roommate living situation entirely for social reasons, as this seems to be a tough city to make friends in.

My ideal situation would be to have my own bedroom/bathroom, high end furnishings, but a shared living space (living room/kitchen). But alas, most people have roommates entirely for economic reasons, so this seems to be tough to find.