It's a Bosch SGI 5305 GB/13. I got an Email back from Bosch and they reckong it could be the control unit which should be easy enough to change but still costs about £95.00! Still less than a new dishwasher though!
Good question, the only problem is I'm not sure where to find it. There was a thermostat on top of the water heater which is brand new so I assumed that would be the only one. I'll look a bit deeper. Thanks for the tip.
For a couple of weeks now the dishwasher has been running exceptionally long cycles and the water has not been getting hot either to wash the dishes or to dry them. I replaced the Instant water heater but no luck, it still doesn't give me hot water! I got the complete unit so it had new...