How can I fix my Hotpoint DWF31 dishwasher?

I am experiencing an onging problem that when the machine is switched on the timer keeps reverting to display a 2 hour time and then seems to start the wash process immediately and then after 2 hours the time reduces to the time selected and continues the cycle. The water does not seem to be heating and by the time it finishes after some 3 to 4 hours the drying temperature does not feel as hot as it did previously. Any help would be appreciated or it looks as though it is a throw away and replacement job.