Even when your car has no spare I would buy a spare wheel/tyre and keep it at home. Then in the event of a puncture you have the option of recovery home without the aggro of finding a replacement tyre in a hurry. This year I had a puncture at noon the day before I was booked on a 6am Channel Tunnel crossing. Paul Harris Tyres had me fixed up the same day but at a weekend it woud have been a problem