Thanks for your comprehensive reply Ventura.
No, I wish it was something as simple as volume tuned down.
If I press the Set register, the display changes from ,say, 445, to 11 flashing. It then returns to 445, with the original sounds.
This happens for all 9 registers with the flashing no. incrementing. It also is the same for the 4 user sets.
This would indicate to me that it is trying to switch to the sets but they are either empty or damaged, so it reverts back to the original setting.
The User Program has 10 sets of various combinations, mostly of no use to me, which the seller may have used for his demonstrations.
One thing that struck me. After performing a factory reset, you have to switch off and back on again. If the coin battery is dead, then maybe it will have some affect ?
I will research changing the battery and see if it makes a difference.
I', going to ring the seller at the weekend to get his e-mail address, although I don't hold out much hope of a solution.
The annoying thing is, I was in France for 2 weeks at my house there but didn't get much time to play with it. If I had noticed then, I could have called on the seller on my way back to the UK.
I inclined to think that the Richard Noel sets may be my way out.