Kev - looks like your core support is low, also, I don't see the lower baffle, not sure if it is the angle or what, but it there are usually tie rod supports from the lower baffle to the core support and the grill frame attaches to this lower baffle to give it stability and stiffness.
The grill is not designed to hold the fenders apart, the baffle does this, once it is in place the grill should fit much better.
