After spending a while looking at it they discovered rust residue in two of the solenoids. They asked where I got my gas, as they said this can happen when people fill it from home gas tanks. I assured them that all the gas I got came from the two local Texaco garages in Coleraine.
Well, anyway, they replaced the two valves, and reset the ECU so we were on our way.
The ECU reset means we need another trip back, as the automatic learning program has to start again. Let's hope it goes better this time!