Thanks for all your suggesstions. I went and purchased a crank, cam and coolant sensor and took to my local garage for them to fit (I don't have time!)
Took it for a spin afterwards and within a few miles, exact same problem! lack of power, ECU light came on and car wouldn't start after I parked up. Tried a few times and eventually started up, so went straight back to the garage and asked them to check the fault codes. Same codes came up. Then the car wouldn't start at all after many attempts, so I've left it with them and they will investigate in the morning...
Took it for a spin afterwards and within a few miles, exact same problem! lack of power, ECU light came on and car wouldn't start after I parked up. Tried a few times and eventually started up, so went straight back to the garage and asked them to check the fault codes. Same codes came up. Then the car wouldn't start at all after many attempts, so I've left it with them and they will investigate in the morning...