WHen I moved here, I moved in with my hubby who was then sharing a flat with three other guys. We lived there about 6 months before finding our own place, but my experience wasn't too bad. As with other things in life, experiences will differ greatly depending on a million different circumstances.
However, I can tell you that flat sharring is very common in the UK, and especially in London where the prices of houses are just too high for most people to live on their own. A good source for finding a flatmate is the TNT magazine which is actually a recruitment magazine but also has adds for flatsharers.
Good luck!