Hi William,
thank you very much for the reply, it has given me somewhere to start looking. I am going to make a test stand for the movement today as I can only run it in the case at the moment and this is proving to be a bit of a pain. I will mark the teeth on the escape wheel and then see if it goes out of beat in the same place each time, If it does then that would indeed mean the escape wheel is causing the problem. I had a good look at all of the wheels as I went through cleaning the clock and they all looked to be in very good condition. There was some wear to the pallet faces which I polished out but certainly no more wear than I would expect to see in a clock of this age.
i will have another look this evening and get back to you if I find a problem.
Thanks again 
Paul.
