I went down to Swedish Day and spoke to Joe, the mechanic who is doing theMOT and service next week. He suggested that I shouldn't rule out a poor connection, so I went out to try and locate the connector on the front edge of the fuel tank. I think i have found it, but I'm not sure. It will only be readily accessible by removing the under tray and getting under the car. The connector I have found looks exposed and ripe for a poor connection, but although it's in the right place and the blue/white wire in the end corner pin looks OK, there is no wire in the the adjacent hole. Which is not matching the wiring diagram in WIS.
I won't have time to do a full check as I'm quite busy between now and the MOT time. As long as the car passes, I will deal with it later. Get the car in the air and do the undersealing at the same time. It looks like the underseal is needed