PG Glass damage car with zero integrity

My insurance arranged that PG glass come do a windscreen replacement at my house. Before starting installation inspection photos of the vehicle was taken. The vehicle has on the bonnet a three piece plastic airvent intake grill. The small piece infront of steering wheel had a crack in however after installation the big centre piece was shattered and when driving to the shop the small piece on the other side flew of and the vehicle behind me drove over it. You can see clearly the clips were broken off, when brought to their attention they refused to take liability for it. I am a fair person and can understand that the initial cracked one would be a problem however what about the big piece that was 100% and the other small piece that is 100% their fault??? A person would think that PG glass is the best and biggest in the bussiness however it is shocking to see that they can break your car and just don't care to rectify their mistakes. Would never ever recommend them to anyone.