I found it on eBay. It was £60.
I was getting a bit desperate cos couldn’t get a new board anywhere, even the manufacturer wouldn’t sell the PCB only.
I could only get it new as a kit with outer case, and a keypad. Wasn’t going to pay that cos I’d already bought a new keypad thinking that was the problem.
I suppose I was taking a bit of a gamble that it was fully functional, but there are some honourable people out there.