In my opinion, the car will be written off as beyond economic repair. Rear quarter panels, unlike front wings, dont simply unbolt. At the least, bumper, bootlid, light and a hefty tug on a jig to get the worst of the dent out then a couple of stone of filler. A proper repair would be a rear quarter panel.
Also dubious about the quarter panel/rear door gap..... 
I agree Ht with all the pessimistic views on this, as I think it is unlikely to be repaired.
However, the garage refused to collect the car until Royal Sun Alliance had given them "authority to repair", something which RSA have confirmed is the case. In addition the other party are accepting full blame and costs due to the circumstances, with even them wanting to make offers of compensation to my injured passengers, so is it possible that they will just repair regardless and give his insurer, Hastings Direct, the bill whatever it is?? :-/ :-/ :-/
I bloody hope so!
