I will be at London for 3 months. My current mobile phone is not blocked (LG KF600d, GSM/GPRS/EDGE, 850/1800/1900 MHz). When in London, I will make few local calls and rare international calls back home. What would be the best Vodafone plan for me?
Go to any mobile phone shop and get the cheapest SIM card you can. It doesn't have to be Vodafone.
You'll also find that if you want to call abroad you can buy phone cards from most newsagents which allow you to phone abroad cheaper by typing in the number on the back of the card before you call. There are so many of these so ask the person selling them which is the best one for your country.