Land Rover Repair: 2004 Range Rover, blown head gasket, coolant hose

Question
I recently had an oil change and within a few days it lost compression driving on highway and died before I could pullover.  Upon looking under the hood the top radiator hose was off but factory clamp and hose had no damage.  It lost all coolant and I checked the oil and was full and had no coolant mixed in it.  I noticed oil leaking under car and I looked under to see a massive amount of oil spread all over the underside of the vehicles frame and under carriage.  It seemed it Sahara come from the rear seal location and around the drain plug that appeared cross threaded.  The service company came and inspected the car and concluded it was a blown head gasket and warped heads from the car overheating.  They also confirmed the oil was full but they used regular oil instead of synthetic oil the factory recommends but didn't know why all the oil was all over the underside.   An independent mechanic confirmed it had blown a seal from overfilling with oil.  My question is do you believe the blown seal and warped heads are related or seperate incidents happing at the same time in sequence?

Answer
There is no way to speculate about how your failure may have unfolded from the scant written evidence.  I'd have to have the truck here for that.  Sorry I can't tell you more.  

There is no obvious reason why an improperly done oil change should result in a coolant hose coming apart.

However, if the oil change place conceded they put the wrong oil in the car they will have a hard time arguing that the whole failure is not their fault simply because they have admitted incompetence in doing the basic service.