Re: "low-priority" for what?
Telecoms operators are subject to a lot of regulation on what they can and can't charge for coming from the EU, like termination charges, roaming charges etc.
these make a big impact on their revenues along with the fact that they are all owned by overseas entities (in whole or part) O2 and GiffGaff by Telefonica (Spain) 3 by CK Hutchison (Hong Kong) Virgin by Liberty Media (USA) SKY by Fox (USA) EE by Deutsche Telekom and France Telecom (Germany and France) along with BT
of the top ten in the uk 2015 only Vodaphone Lyca and TalkTalk are uk owned and only Talk Talk relies on its UK operations for the most of its revenue.