Testing across the mains filter that is at the back of the machine, immediately
connected to the incoming cable, gives:-
E-L = 330 M Ohms
E-N = short (0-ish Ohms)

That shouldn't be like that Earth to Neutral short if the machine is
disconnected from the mains unplugged..

Try that again and report back with the machine unplugged.

If there is an E to N short than these the cause of the problem its one
of those barsteward leaks that won't trigger till you get some current
flowing.

The usual cause of tripping is a Live to earth short in the water
heating element had this more than the once!..

But this filter, can you pull all the leads of it then run those ohms
checks again, make a careful note of which wire goes where or take a pic
of it!.



If I disconnect the front control panel then plugging in the WM doesn't trip the
RCD. But if I reconnect everything back up, then it trips immediately.

I'm afraid I don't know enough about those filter things, but is that E-N short
correct? Could it be the filter that's duff?

The control panel has a big sealed switch for the main control know, so I've no
idea what the contacts are like inside. Moreover, I don't know if it's possible
to buy another panel (economically at least) or if it's just time for a new
washing machine.

Thanks again gents for all your expertise. Hoping someone might know a next
step to try.

--
Tony Sayer