I would suggest you start by removing the door card and disconnecting the window switches, and see if the issue occurs. if it does, it indicates the fault is on the wiring circuit, so you need to check for water ingress at the door, or damaged wires. Alternatively the issue may be elsewhere in the loom, but this is the best place to start looking.
Thanks for the good advice.
However, the problem only happens about every 3 months, so it will take a long while to see if disconnecting all my electric windows has sorted it
I really needed to see if this was a common fault with a recommended fix.
Not sure it's worth spending £144 or so on a 140k mile Mondeo.
I'm off for a 250 mile motorway trip tomorrow so the engine & exhaust will be nice & warm & hopefully burn off all the crap I've deposited in there recently.
OK. I see it might cost around £100 or so for a 2 litre diesel.
I'll still try an Italian Tune Up & intend to use Shell VPower Premium Diesel every few tankfulls.
The mileage I do means Premium Diesel would cost me about £75 extra a year if I used it all the time. If I use it 1 in 3 times it would cost as much as a Terraclean every 4 years. I can't see the car lasting that long...!