So a local garage had a closer look today, and said the vibration/knocking, was down to the water pump and drive belt tensioner. Replacing these parts and some fresh engine coolant, left me £218 out of pocket. For parts and Labour is this excessive? My Dad reckons not as main stealer prices may charge 2.5-3x more....

The starting issue isn't said to be an engine fault from what the diagnostic system reports...more the Alternator to blame and was noted the Alternator Drive Pulley is somewhat noisy. And the Radiator could be leaking

All these issues on a soon to be 6 year old Car with 36k on the clock is a bit poor surely?