Check if your insurer provides a multi-car policy and then just add the new car onto the existing policy. Do not use temporary insurance. Alternatively, contact your present insurer and ask them for proof of no claims (which they have to give you). Use that on the new policy, whilst keeping the old policy open until you sell the car. You have a 14 day cooling off period on your new policy. If you have not sold your car, cancel it and re-insure with another insurer. This will give you time to sell your car whilst having both cars covered. I will no doubt get a load of complaints from insurance bods, but no reason why you cannot. I would not suggest doing this long term though, couple of weeks at the most.