Electrolux Dishwasher not heating / drying. ESL5201LO

Well difficult from the end of a computer can be difficult onsite! So pointers only. I`d have a look at the work you have already done before doing anything more otherwise you will start chasing rainbows. Presume the water level is correct? Presume the wash motor comes on and sounds normal- that bit is important, if the water level is not enough change the pressure switch? The part you mention as thermostat is not on the parts breakdown as a thermostat!! If you fitted part 140000401061 that is a turbidity sensor not a thermostat since the actual thermostat/s as far as I can tell are part of the heater unit that you fitted part number 140002162232.
What you then want to do is to check the wires from the pcb to the heater, so remove the decor wood door and remove the outer metal door panel. Where the wires can break is where where they stick to the tar noise insulation and sometimes where the wires disappear under that plastic cover on the right. Failing that then have a look at the pcb for a unsoldered/dry joint on one of the relays. If there is one at least that should be it if it all visually looks normal = a big delema since a preconfigured pcb is listed at £136 part number 973911539139056. Only thing I can suggest. Do not buy anything as yet as perhaps someone else may add another suggestion.