Cheers for coming in Dave. Would seem that you may be right. I’ll reverse the change and confirm if that takes the fault code away. Then it might be back to square 1 to have the thermostats located and swapped.
I did have a look online to see if it was subject to recall after hearing on the news that there are units that are a risk, but the model number was not exactly as mine. I will double check though.
Much appreciated.