Beko dishwasher not heating properly

Hello I am new to these boards so will try and explain my problem as briefly as possible. I have a Beko Slimline dishwasher DL 1043W and just lately I have found that sometimes it works absolutely fine, but other times it won’t stop washing and the water doesn’t seem to heat up properly! Could this be a faulty thermostat? If so I wonder if anyone on here knows where the thermostat is located on the machine, and whether it is fairly simple to change it for a new one?
Thank you in advance for any help over this.