Thank you for your advice but I don't think it is the solution. There's about a cupful of water in the sump and the pump is pumping to the rotating arm and not out of the machine. I need to carry out some more tests to give you a better picture. Give me a day or two.
Kevin, I think the problem was electronic. I had tried re-setting the machine previously as per the instruction book but I wasn't getting any response. I left the machine plugged out for a day or so as I had other things to do. When I got back to it yesterday and plugged it in, I went through the process of re-setting and the machine responded as per the book. I then ran 2 different programmes and monitored them carefully. They both ran perfectly.
I can only conclude that the machine had a bit of a brainstorm mid-cycle as it was trying to wash (or rinse) with only a cupful of water.
Turning it off then on again doesn't seem to clear the memory straight away. I think it needs to be off at the plug for a number of hours.
This is probably a rare event which hopefully won't happen again.