Audi TT auto - Coolant Temp Sensor and now not running

[PG35]

Had engine management light come on with the fault code for Coolant Temp sensor last Fri. Only driven it 20 miles back from my mechanic and it's been sat on the drive. But then went to turn it over this morning and battery levels etc are fine but its not wanting to start. Any advice??? It's had been running rough in lower gears for a couple of month with no warning lights etc prior to this and it had water pump and cam belt done 6 months ago.

[cuprabob]

It could be the crank / engine speed sensor but best get it scanned again to see what faults are now recorded. I don't think the issue is related to your ECT sensor change unless the mechanic disturbed something.