I have just been outside and tried to open the doors with the central locking and the back ones popped but the fronts didn't it must be cold ? i finished up using the key to work the central locking  ::) :y

Happened to my VW Caddy van on Thursday evening ......

The drivers door was actually frozen to the body.
To make matters worse, I got in through the passenger door, and in the ensuing mayhem, snow fell off the roof on to the passenger seat ..... !

Drivers door released yesterday morning by spraying around it's edges with a whole can of de-icer. Try a light coat of petroleum jelly on the surround rubbers - should do the trick!