List of UK mobile SIM providers, cheapest prepaid SIM, Free PAYG UK SIM

There are many mobile companies operating in UK. Some of them are very popular and expensive and some are really cheap. If you are looking for the list of all companies then you are at right place. Please go through this article to find the list and their websites.
Vodafon UK
T-Mobile UK
Virgin mobile
Orange UK
3-UK (Three mobile)
O2 UK
Lebara mobile
Lyca mobile
Vectone mobile
ASDA mobile
Tesco