Hi fairy! I've been flatsharing for many, many years and in many different places and have never had a lock on my door. But it just depends on a few things. Is it a busy place with lots of people coming and going? In which case I would probably get a lock. People have on the whole respected my space and in fact the only problems that I have encountered that spring to mind was when I have lived with the owners who obviously believed that as it was their property they could just wander on in! So it is a policy of mine to never live with the owner! Also if you are worrried about burglars they will just kick the door down anyway.