[B10alia]

Welcome!
I've never heard of the 2.8 diesel before, and I've never owned or worked on a diesel car. This opinion is coming from experience on gasoline engines.
I don't think that a piston strike could destroy a con rod (that's what I assume happened). It takes a lot to break those-- think about it this way. My Dodge has a 2.5 liter, four cylinder engine that makes about 100hp. That means each cylinder is responsible for about 25 of those horses. One piston, pin and con rod for 25 horsepower. This is in an engine that has an 8.9:1 compression ratio or thereabouts. When you consider that diesels typically run 20:1 or higher, you get an idea of how much stronger the components are. The valves, however, aren't really that much more substantial in a diesel, because the only force on them that really increases is the force pushing them against their seats. So you have a stronger lower end hitting a top end without nearly as much strength in comparison to the relationship between bottom and top end in a gas engine. I have never heard of this happening in a gas engine. The only way I could really see it happening in any engine is if the face of the valve went into the cylinder and got stuck so it was taking up a substantial amount of room. Even then, the cylinder heads are much softer than the crank and connecting rods. I would think that the tendency would be to ram the sideways valve into the head. You'd see significant head, piston and valve damage, but I doubt you'd have damage further down.

I would be looking for another garage if I were you. It certainly sounds like the mechanic you have is doing sloppy, careless work. An engine that has had a piston strike needs to be carefully examined, particularly the head, valves, cam, AND cylinder bores. The engine needs to be gone through to make sure no pieces have come loose and ended up in the engine. That's what it takes, and I would be DOUBLY sure to make sure EVERYTHING in the engine is OK before releasing the vehicle if the piston strike resulted from poor work on my part previously, as it seems here...

 

[ImperialCrown]

What a mess. The best way out would be to find a good used or remanufactured engine. This one may be too far gone to recover with any degree of reliability, but if an exchange motor can't be found, it would have to come out for rebuilding. If the block can be saved, the engine may be rebuildable.
If you are looking for compensation or liability on the part of the shop that may have been responsible for damaging the engine, you would need documents (and possibly witnesses) stating that what they found in their diagnosis led to the belief that the other shop was negligent or otherwise at fault in their service that led to the engine failure. Discuss this with an arbitrator or lawyer? I am unfamiliar with consumer protection laws in the UK.
The back of the shop repair order page (hard copy) would have the technician's notes, findings and actions and could bolster your case. Especially the timing being off, which may have precipitated the end failure. This co-operation may be difficult to ask for, but it never hurts to discuss this with the shop. Will they 'go to bat for you' or provide you with documents and testimony that would be favorable to your case, if needed? The worst they can say is no.
I have been called into court to testify on what I have found with a vehicle, but was reluctant to place blame. The root cause of the failure was too variable and a couple of 'chains of events' may have taken place. I could not tell the court what exactly happened, but that it did happen. The vehicle's past history was unknown to me. The documents provided were too vague as well. The plaintiffs were relatives of the dealership management that employed me.
No one wants to (or can afford to) pay thousands for an engine repair, especially when they placed their trust in a facility to do the right thing. Best of luck to you in this situation.

 

[madmaxjeep]

Welcome!
I've never heard of the 2.8 diesel before, and I've never owned or worked on a diesel car. This opinion is coming from experience on gasoline engines.
I don't think that a piston strike could destroy a con rod (that's what I assume happened). It takes a lot to break those-- think about it this way. My Dodge has a 2.5 liter, four cylinder engine that makes about 100hp. That means each cylinder is responsible for about 25 of those horses. One piston, pin and con rod for 25 horsepower. This is in an engine that has an 8.9:1 compression ratio or thereabouts. When you consider that diesels typically run 20:1 or higher, you get an idea of how much stronger the components are. The valves, however, aren't really that much more substantial in a diesel, because the only force on them that really increases is the force pushing them against their seats. So you have a stronger lower end hitting a top end without nearly as much strength in comparison to the relationship between bottom and top end in a gas engine. I have never heard of this happening in a gas engine. The only way I could really see it happening in any engine is if the face of the valve went into the cylinder and got stuck so it was taking up a substantial amount of room. Even then, the cylinder heads are much softer than the crank and connecting rods. I would think that the tendency would be to ram the sideways valve into the head. You'd see significant head, piston and valve damage, but I doubt you'd have damage further down.

I would be looking for another garage if I were you. It certainly sounds like the mechanic you have is doing sloppy, careless work. An engine that has had a piston strike needs to be carefully examined, particularly the head, valves, cam, AND cylinder bores. The engine needs to be gone through to make sure no pieces have come loose and ended up in the engine. That's what it takes, and I would be DOUBLY sure to make sure EVERYTHING in the engine is OK before releasing the vehicle if the piston strike resulted from poor work on my part previously, as it seems here...

 

[madmaxjeep]

Thanks for the replies - I think the valve and piston strike sent a shock wave down the con rod and damaged the big end bearing this then lead to low oil pressure which in turn lead to crank shaft damage, I have had the engine rebuilt by a VM Diesel Spcialist who says that the big end on cylinder 3 was damaged the rest were worn but ok for the mileage I had done. They have completely stripped the engine down and replace any damaged or worn parts and rebuilt the top end with new cam belt and timed it all up correctly I hope - I did not trust my garage to do this after the mess they made first time round - they also wanted silly money to rebuild the engine - some £9000 - the jeeps only worth £4000 max. The rebuild at VM was £2000 inc collection and delivery. Now waiting to have the engine put back in a see what the results are - after 6 month I have forgotten what it drives like!