Petrol into a modern diesel engine will probably destroy the injection pump and injectors. You can be lucky on occasions and get away with it depending on how long it drives for, how much diesel was in the tank etc.... If you are lucky then it's a simple case of drain the tank, change all the filters, and flush it all through. The worst possible case I could think of would be destroying the injection pump, injectors, changing the rail and pipes, fuel pickup, fuel tank sensor and that would normally be it. Can't think of a way that it would lead to anymore damage. £9k seems very steep!
I think I'll stick to a nice basic landrover engine!
HTH
Ed
Diesel FIE Development Engineer