Yeah not sure where you're all getting the idea that his insurance will fix it and chase it all up etc...That's exactly what third party does not give you..
Third party, you hit someone and are at fault, your insurance fixes their car, you fix your own car. Someone hits you and they're at fault, their insurance handles it all, your insurance has nothing to do with it..
Full comp, call the kunce and tell them to fix everything, now.
Tell this mother f**ker that the damage to his skull was pre existing and not a result of you caving it in with a f**king brick