siemens se25a090gb/17 pre-soak light pulsing no display, wont work?

Purchased 2nd hand dishwasher, ran a rinse cycle to clean it, seemed ok, then selected 35 degree quick wash. After a few minutes opened the door and the machine had filled with water but nothing was happening and the tablet had not released.
The pre-soak led was now pulsing (this had not been selected) but it is not possible to select any other button and the machine does nothing: the only thing working is the on/off button. Have tried to reset as per manual (holding 2 buttons simultaneously for 3+ seconds) but this has no effect. Also switched off at mains to reset but again nothing. Dishwasher engineer said the heating element had gone and blown the control panel and therefore uneconomical to repair but not convinced he is right.
Would really appreciate some help. Many thanks