Good afternoon this sounds like a fault with the PCB\control board.
This will most likely need to be replaced, can you please advise of your postcode and I can look to cost up the cost of a part and engineer.
The engineers have left for the evening, I will aim to get back to you tomorrow morning if that is ok?
Just to update you the cost of an engineer is around £52, they have advised the fault may be to do with a heating issue, which could be a thermal sensor, or just the PCB not handling the input from the sensor properly.
The engineer is going to come back to me with a estimate for parts, at which point I can then pass on his details to arrange a visit if you wish to proceed.
I would suggest you use ADS, who can be contacted on 01235 818598, we have referred customers to them numerous times and always had good feedback.
They have availability to come out this week, and charge £52 in labour, based on the fault they estimate the parts cost will be £98
Please let me know if I can be of any further assistance, and I would appreciate if you rate the service received.