I think everyone is struggling to find good people to do work, anyone worth their salt is booked up, I've just booked the car in for some investigative work (probably an hour and a half), 17 September is the earliest they can do and it's taken about two weeks for them to consider what was needed. They came highly recommended but we shall see .....
It's difficult to answer on the info you've provided? Covering up walls suggests you have some leaks, which generally only get worse the longer you leave them.