In reply to mypyrex:
> Surely not possible when you're driving from A to B and using the tablet as a satnav?
Fair enough. You will therefore be at the mercy of your tablet and the ridiculous prices charged for roaming. Certainly disable any form of app updates, podcast downloads and other under-the-hood data usage.
One word of warning though. If you are using Google Navigation it does kind of conk out if you loose the signal. I tried to use it when cycling from Shrewsbury to the middle of knowhere in Shropshire. All was going well until the last 5 miles when I lost the signal and all hope of finding my destination. Fortunately I managed to work out where I was from a very blurry map that was left.