2005 Ford Mondeo Ford Mondeo 2.2 TDCi clutch

My Mondeo 2.2 TDCi Estate (05 reg, 55k miles) just came back from an accident repair under insurance. 24 hours later after 100 miles we had to be recovered from the side of the road because the clutch went. It appears there's a hydraulic fluid leak from somewhere. The repair garage insists it has nothing to do with damage caused by the accident, or their repair work.

So, over to you - please tell me, is the leak from "natural causes"? Is it a coincidence? Do I have a claim against the insurer/repairer?

This is how the original accident happened:
A large piece of brick or stone was bouncing along the carriageway and went through my front grille whilst travelling at around 70mph. It momentarily bounced around under the car before exiting somewhere at the rear. The front deflector and grill went under the car, and the underskirt touched the road and went completely under the car making it undriveable. The car was reversed to bring the underskirt back to the front of the car. The car was recovered back to Sussex from Cumbria.

They replaced the following:
1322638 Bumper Assy
1205717 Deflector
1346073 Grille
1301038 Housing
1346677 Jet
1313503 Intercooler
1034869 Clip