Personally I'd take it straight back to the mechanics and tell them to sort it out at their expense, and have it valeted inside and out.
They sound like a bunch of cowboys.
It's going back to them at the weekend, I've stopped driving it but I can't take time off work to take it there. If he can't fix it without fucking it up again I'm loading it up with oil and driving it down to Winchester to Skuzzle.
Personally I'd take it straight back to the mechanics and tell them to sort it out at their expense, and have it valeted inside and out.
They sound like a bunch of cowboys.