Having the flat cleaned at the end of a tenancy is the best way to ensure that the removal is not too much of a nightmare I find. You can get stuck with the cleaning at the last minute, and then run out of time before you have to be out and drop off the keys, and that is super stressful, especially if you put down a massive deposit. My last landlord was a bit of a nightmare, but I got Cleaners Bermondsey round to clean the place before I left, and he had no reason to charge me for anything, as the flat looked better than when I arrived!
