Its a victorian terrace and a rental house, so I dont want want anything too expensive. The existing door is an old aluminium DG door, its OK apart from the lock which is broken. Apparently it can be replaced but not with a multi locking lock (ie not very secure) and will still cost £200. New UPVC DG ++ and ugly, so need what else and where from?
Get a solid wooden door, fitted with a BS deadlock and a BS nightlatch. It will be cheaper and more secure than a plastic door, and will last a hundred years longer. It will be easy to change the locks when necessary without special skills. Unlike a plastic door it will not go wrong.
If the frame is rotten or in poor condition change that too.
A joiner or carpenter can fit a door and frame much better, and more quickly, than a handyman.
There is a British Standard for thief-resistant locks. A BS 5-lever mortice deadlock in a solid wooden door is about as good as you can get, and not at all expensive. Supplement it with a BS nightlatch at shoulder height.