Once the car is officially written off you can get on with ordering a new car and starting your three year lease again (as long as you have 12 months PIP remaining). From the point of write off its quite straightforward, the only challenge being finding an in stock car or waiting for delivery.
When mine was written off I did not take the courtesy car or taxi and was refunded any PIP money, but I am able to drive any car so was able to use a family car on the odd occasion when I really needed something and there was nobody available to give me a lift.
Good luck with it and sorry to hear about the horrible experience