In a couple of weeks, I will be moving from the US to the UK for a year. Upon researching cell phone plans, it seems the most cost efficient option is to take an unlocked GSM phone with me and purchase a prepaid-SIM card or use a month-to-month plan. I have always used CDMA providers in the US, so I need to obtain a quad-band GSM phone. I am considering purchasing a used US-version G1 phone and then getting it unlocked. If I do this, 1: Will I be able to use this unlocked-G1 phone in the UK? 2: Can the unlocked-G1 be used with any cell phone provider or does it have to be T-mobile Europe? (For example, can I use it with Vodafone or O2?) 3: Can I use a prepaid SIM card from another European cell phone provider (such as Vodafone)? 4: Are there any features that won't work if I do this (such as web access, GPS, etc.)? I appreciate any help you can provide.