Thanks Dave. There is a channel inside the machine from the filters at the front of the dryer to the reservoir at the back – which, I guess is equivalent to the pump hose .
I’ve blasted water through it with a Karcher and a great deal of gunk came out. This was a bit drastic but it was the only way I could clear it – and it looks like it has worked.
Hopefully this will have been the cause of the problem and I’ll run a test cycle later today.
Thanks very much for your help.
Chris