Cheers
The contractors rang me in the end and it seemed to go more smoothly. They were a bit late but the job got done at 6.00pm yesterday.
I'll have to wait and see if they refund the second fee that they took by mistake.
I have to say that the call centre has improved. Judging by the accents the people I spoke to were in Scotland and they seemed genuinely concerned by my problem, even when I was ranting.