I bought a SIM card from Telestial before I took my UK trip because it has received some good reviews. My experience with that little SIM card in UK turned out to be a total nightmare. I had to make numerous calls just to get it activated. The customer service hotline that supports the SIM card in the UK is not 24/7 and the service was horrible. It took more than 3 days to get the SIM card activated and registered on the network. When I finally get to use it to phone home in the US, all US numbers (as it turns out) were blocked. I am still trying to communicate with Telesial and Mobile UK which supplied the SIM card to get the problem resolved. Next time when I travel to UK, I think I will just try the local kiosk there.