Kenwood KDW243A dishwasher won't start?

When I switch on my Kenwood KDW243A the number 20 appears on the display,if I leave it like this nothing more happens,no amount of button pressing changes anything.
But if I switch it on and push and hold the "clock" symbol button at the same time all lamps flash if I then push "P" the display goes to "18" then "17" the pump runs momentarily and water enters the machine.
"16" appears and the machine starts to wash the "15" appears and it stops washing,this cycle continues in a countdown type of way until the display reaches "10" and everything stops and will not start again until I repeat all of the above.
Upon opening the door the machine is wet inside and the detergent flap has opened..any ideas ??