I haven't a clue what is involved in changing a turbo. But I would think anyone competent to do the job with a guarantee is worth every penny of £40 /hr. One of my local dealers could probably do it a little quicker...but he charges £80/hr. It could be as easy as changing front discs, just a jigsaw in reverse, just undo this and tighten it back up, but then, perhaps not. So pay the man