I was travelling to London a few months back, I thought of picking up a local prepaid SIM at the London airport itself until my friend suggested me to buy a Matrix international sim card instead. She had used their student plan and had good things to say about their services. Also she said that they are supposed to be cheaper than the local ones in the country. I contacted Matrix cellular services and was surprised to see the overwhelming response and the offers that they provided during my 21 day stay in London. I must say I am a happy matrix customer since I landed up spending minimal from my budget on getting the sim. Thank you so much.