@loulou2012
...car engine cooling pie and head gasket effectively blew up and destroyed the engine..
From your description, it is impossible to tell if there is any liability on the garage.
For a start, what age is the car and how long have you owned it?
On a new car, you would not expect a pipe to burst ... anthing over 3 or 4 years old, it is a mechanical failure on a vehicle you own so it is just the same as any other mechanical part failing.
If you only bought the car from a garage/ dealer... even though it is older, then you may have some comeback. If you bought privatly, them caveat emptor (buyer beware or you bought it as it was/ sold ad seen....ie your responsibility!)
If a pipe burst, them pipes are not inspected in general at a service. Yes, the mechanic will visually pick something up if it is obvious... but a pipe could be rubbing in a place not visible, or perishing and not obvious to the eye.
Also, if a pipe burst, was there not a warning light that came on to warn you the coolant was low or temperature too high?
If it wasn't a pipe burst, whay was the cause... and did the garage do any work that may have caused it (had a wster pipe off for another job and didn't tighten pipe, changing coolant and left air in system or didnt fill it etc).
So many factors to consider before anyone could tell if there was any liability on the garage or just an unfortunate coincidence.... and more importantly what are the chances of successfully persuing the garage for damages.