Just because an operator is listed here does not mean we endorse its products and services.

I've put together a list of mobile operators in the UK:

I'm still working on this list. If you have anything to add, please post on this thread.

Operator	Network	Notes
3	3
360 Mobile	3
ASDA Mobile	Vodafone	Will be changing to EE.
Banana Mobile	EE
C Mobile	EE
Delight Mobile	EE	Part of Mundio Mobile
DobryTel
Donate Mobile	Vodafone
Econet Mobile	EE	Econet Wireless International Group.
EE	EE	The letters stand for "Everything Everywhere" and it was formed from the merger of Orange and T-Mobile.
Epian Angel SIM
Family Mobile	EE
Freedom Talk
giffgaff	O2
Globalgig
GT Mobile
iCard Mobile	Vodafone
iVitta Mobile
Kite Mobile		Home page states offer that applies until 30th September 2011!
Kontakt Mobile
Lebara Mobile	Vodafone
LIFE Mobile	EE	Run by Phones4u
Lycamobile	O2
Maxroam
Mobile by Sainsbury's	Vodafone
Now Mobile

Operator	Network	Notes
O2	O2
Orange	EE	Part of EE which was formed from the merger of Orange and T-Mobile.
Samba Mobile	3
Shebang	3
SIM4travel		Issued with 07-allocated Jersey Telecom number.
SIMFINITI
Simple Call Mobile	EE
T-Mobile	EE	Part of EE which was formed from the merger of Orange and T-Mobile.
TALK HOME Mobile	EE
Talkmobile	Vodafone	Part of Carphone Warehouse
TalkTalk Mobile	Vodafone	Part of TalkTalk and only available to TalkTalk customers.
Tesco Mobile	O2	50:50 joint venture between Tesco and O2
The Co-operative Mobile	EE	Run by The Phone Co-op which also operates The Co-operative Phone and Broadband.
The People's Operator	EE
Truphone
Utility Warehouse	EE
Vectone Mobile	EE	Part of Mundio Mobile.
Virgin Mobile	EE	Part of Virgin Media.
Vizz Mobile	Vodafone
Vizz Mobile Africa	Vodafone
Vizz Mobile Roshan	Vodafone
Vodafone	Vodafone
White Mobile	EE
Wildlife Mobile

Business only providers (as far as I know — let me know if you know different):

• Abica Business Mobiles
  
• Anvil Mobile
  
• Axis
  
• Consega Mobile - Uses 3 network.
  
• Digital Spring Mobile - Uses Vodafone network.
  
• Gamma Mobile - Uses Vodafone network.
  
• Podsystem
  
• Skyrack Mobile-X
  
• Smarter Mobile
  
• TeleWare Mobile
  
• XLN Telecom Mobile
  
• YooZoom Mobile
  
• Wireless Logic
  
• Worksmart Technology

i Card run over Voda.

Lebara run over Voda.

LycaMobile used to offer a service on Orange using 075 numbers but has now phased that out and only offers its new LycaMobile Plus tariff that uses 074 numbers and the O2 network

Utility Warehouse runs over EE.

As well as Talk Mobile ,their is TalkTalk Mobile part of TalkTalk runs over Voda i believe.

http://mobile.talktalk.co.uk/

A long list of UK Mvno can be found here : http://www.prepaidmvno.com/mvno-companies/eu-mvno-companies/uk-mvno-companies/#0207

Thanks for the follow-up bigjohn. I will look at getting others added to the list.

I'm very surprised at how many virtual providers there are out there. I was kind-of expecting to have a list of maybe twenty-or-so.

The article Realm of the MVNO from Mobile Business Magazine makes interesting reading. As well as MVNOs there are MVNAs (mobile virtual network aggregators) and MVNEs (mobile virtual network enablers) that are the link between the smaller MVNOs and the (MNOs) mobile network operators. They allow MVNOs to start up as they have the purchasing power that a new operator alone would not.