We just had 2 snakes shipped to us from halifax. they arrived alive because they were packed well. they were in their own little containers (plastic sandwich containers with holes), placed in a styrofoam box (like a disposable cooler) with newspaper to keep them from bouncing around too much and a bottle of hot water to keep them from getting chilled. the styrofoam box was in a tight fitting cardboard box that was well taped.
also they were shipped same day, as live animals (which means they get the heated cargo hold and waiting area on arrival). You will pay extra, but so what?
If you have your own vehical i'd suggest going to london and picking them up, the time ends up being the same, what with loading, unloading, etc. and you don't have the flight (air pressure changes, noise, vibration) to stress them.
it's what a 2 hour drive each way?