https://volvodiagnostic.com/ is about an hour round the m25 and up the A13 to Tilbury, so not too far away
they can do programming, if it is necessary
I would drop them an email first and just ask what they think about the fault and if a new/replacement 2nd hand one would be likely to cure it
contact@volvodiagnostic.com
someone else might come along and suggest other things to try like which pins to test for voltage or whatever