Hotpoint WMA50 stoping mid cycle

Since we purchased this machine we have had nothing but problems The machine has been replaced twice but we still have the same fault intermittently .We have had numerous visits from Hotpoint engineers who have replaced various parts ie moter,control module etc to no avail .One engineer suggested the supply voltage was the problem so we fitted a spike protection device again to no avail (we have had no problem with any other electrical device in the house). The Machine seems to stop at random with the wash/rinse spin/final spin lamps lit.We have to press start to enable the washer again.The washer could be ok for two or 3 weeks before the problem occurs again.Any ideas before we take a trip to the tip!