B&Q for sure.
Hope nobody was hurt. I totaled my truck in January, so this stuff is pretty fresh in my mind.
First, repeatedly bang your head against a wall to prepare yourself for the next few weeks/months. Then take pictures of everything, if you can. Call your insurance immediately to file a claim and arrange car rental services. Get the other side's information and pass it along to your insurance rep. Hopefully the police were involved and filed an incident report.
If your car is totaled out, make your insurance take care of scrapping it and they'll cut you a check. If the other side was at fault, save all receipts and turn them in for reimbursement. If you were injured, go to a doctor NOW, even if the wreck was your fault.
Once reimbursed for everything, buy a new car.