You will have to check with your insurance company, some insurance policies don't allow you choice of repairer. If this is the case, your insurer will tell you where to take your vehicle for assessment and repair.
The severity of the crash and the economics of the repair will determine whether the vehicle is a write-off.
A repairable write-off is a vehicle that the insurer has decided is not economical to repair. It doesn't mean however that the vehicle can't be repaired, in this case it may be purchased by someone who can do the repairs more cheaply than the insurance company could achieve.
Yes, most Highbury smash repairers will be able to give you a quote to fix up some minor issues with your vehicle.
If you need smash repairs in Highbury then the best idea is to browse our listings to find a smash repairer near me who can also be used in conjunction with your insurer.