I am thinking if buying an iPhone 3G when they are unlocked so that I can run my Vodafone Pay as You Go SIM on it.

If I were in a 3G area and checked my mail or used the GPS (which uses 3G?) would this charge me money every minute?

As long as the provider (Vodafone) has 3G will it connect on pay as you go? For push e-mail would that mean I would be constantly charged as long as the 3G setting is turned on?