Ignis ADL347 water not heating - Continuous flashing start light and beeps?

I have a fault with an Ignis ADL347 dishwasher. (service #: 8545 347 15410). Wash cycle starts water enters machine but after prewash does not heat - instead there are continuous beeps and flashing start light. Dishwasher reverts to Prewash cycle. At 8 years old would be useful to know whether it's a fault I need to call out an engineer for (could be expensive and not economically viable given age) or whether there are and checks I can do first. Have googled problem and come across various answers... faulty NTC, fault with PCB, blocked pump...

Any thoughts?

Kitchen Chaos
July 2009