Interesting page over on the expansys site which I grabbed just now. They are selling what they describe as an Apple iPhone 3G S (EU, Black 32GB) which is: supplied network-unlocked, i.e. you can use this device with a SIM card from any UK or European GSM network (e.g. Vodafone, T-Mobile, O2, etc.).
It is interesting that it is described as an EU or European model which they will have in stock on July 19. Apple have previously sold unlocked iPhone 3G devices in Hong Kong aimed at the wider Asian market.