Hotpoint Ultima SDW80 dishwasher powers on but won't start?

Hi,

I have a Hotpoint Ultima SDW80 dishwasher which has suddenly decided not to start. It is powered on (the LCD screen is on) but when I press start it just beeps as normal and then nothing happens. The remaining time, 2h25m, just flashes on screen.

I've checked the filters, the water pipe, the filter in the water pipe, etc.

I wonder if perhaps it thinks the door is open but I've tried firmly closing it, etc. I can only assume the door close sensor is in the latch as I can't find one anywhere else. Can anyone help me please?

Thanks a lot

Simon