I have now bought a secondhand Miele from a semi-retired appliance
engineer in South London, giving him the bust Miele in part exchange.

He has taken it apart and found it was the wash pump that has failed -
nothing to do with PCB or dispenser, so i'm going to ask for my money
back from the firm that claimed to diagnose the fault.

I'm tempted to report them to trading standards if they don't refund -
strikes me some of these firms you find on the internet are scams to
sell new machines but they seemed plausible and sent an 'engineer' when
they said they would.