I've just moved into a house which has a large upvc window/patio door with a tilt and turn door fitted. The door doesn't have a lock, just a large handle which operates the tilt and turn. This doesn't seem very secure and I'm sure the insurance woudln't cover me if there was a break in. Is it possible to fit a secure locking mechanism such as a five lever locking handle and where might I find such a thing or are there other options? I've searched Google but not really sure what I should be looking for as it throws up plenty of tilt and turn handles but these appear to be mostly for windows.
Thanks
John