Well, just had the garage back on the phone. They have had the car over a week and I had no contact since giving them the go ahead on the £700 repair.
So I call them today and they tell me the fault they thought it was is not the issue, it is instead another part and this will cost £1000 for the part alone.
I traded in an RX8 to buy a ford 2 years ago as it was more common and easier to fix and I thought more reliable. Since I bought this car 2 years ago it has been in the garage 6 times with various faults.
Time to scrap it I think and buy a brand new car.