2007 SAAB 9-3 Run away engine

On Saturday my car was serviced and MOTed. Apart from a few things (wiper, shock absorbers), everything was fine. After driving the 2 miles home the car started to blow a great deal of white smoke from the exhaust. I turned off the engine and got out of the car but the engine continued to run for 60/90 seconds after, covering the street with thick white smoke.

I called the AA who toed me back to the garage and they tested my oil level which appeared twice as full as it should be. The garage was closed but I contacted them on Monday morning and dropped off my key early Monday evening.

On Tuesday 5pm the garage said it was their fault and that the oil was double what it should have been. The owner was very apologetic and said they would cover all costs.

By 5 pm Wednesday, it was no longer their fault. He said that it was the particulate filter and the timing of being on the day of a service was just a coincidence. He offered to swallow the labour charges but I would have to pay for parts.

Today, he has told me that it is not the particulate filter but the turbo. Again it is just a coincidence that it happened on the day of my service. He has said that 4 of my fuel injectors need rebuilding (£95 each + VAT) and once he gats them back he can see what else needs doing. Again he said he would swallow the labour cost but I would pay for the rebuilding and all parts.

Since he has looked at the car over three days and given me three different diagnostics, I am beginning to doubt him. Is it most likely a coincidence? Is he being kind by swallowing the labour charge? Or is it likely to be the garage's fault and he does not want to pay out any costs?