Hi Martin,
Once again thanks for info. No she's not an A/C model ( as I have more than once wished over the years, especially when in France!).
However, am sure that the relay you have identified will be the one to try swapping so that's a task for today!.

These models certainly have a submerged electric pump as I have had it out of the tank and tested it on a separate battery!.(and it works Ok that way)

I also have a 2000 Mondeo but overall despite the A/C and Power Steering on the latter I still sometimes prefer to use the Sierra - - especially as it's such a good load carrier. I has - even now late in life - a bit more torque for a start compared with the 1.8 Mondeo.

Cheers for now, Richard