Telecommunications was Hutchison's second-biggest business by revenue last year, after retail chains and before ports, according to data compiled by Bloomberg.
The deal will be funded by a 6 billion bridge facility that Hutchison 3G UK Investments has entered into with HSBC Holdings and Hutchison's own cash resources, the company said in a statement to the Hong Kong stock exchange yesterday.
The deal comes as Li, Hutchison's 86-year-old chairman and Asia's second-richest man, is overhauling his business empire before handing the reins to his eldest son Victor Li.
Li is merging his two biggest companies and plans to spin off their real estate assets into a separate unit later this year.
That hasn't stopped Hutchison from pursuing other deals as Europe's telecommunications firms combine to gain more pricing power and amid sluggish economies that restrain the industry's growth.
In Italy, the company is currently in talks to merge its local operations with those of VimpelCom, according to people familiar with the matter.
Revenue from telecommunications services in Europe will probably decline 1.5 per cent this year after falling 2.2 per cent last year, said researcher Ovum. Besides mergers and acquisitions, carriers are pushing for more lenient regulation and introducing faster networks.
"They can drive a lot of synergies" with the agreement deal, said James Britton, an analyst at Nomura Holdings in London.
"Whether that really equips them to be fully competitive in a converged UK market remains to be seen."
Hutchison's agreement would reduce the number of UK wireless networks to three from four. Hutchison is betting on size to compete, taking on rivals that are adding services such as TV and internet access to lure customers.
The deal "will create a business with unmatched scale and strength that will allow us to better compete against other operators in the marketplace," said Canning Fok, Hutchison's group managing director.
With more wireless subscriptions than people, carriers in the UK have been busy preparing for consolidation. Last month, former phone monopoly BT Group agreed to buy Deutsche Telekom and Orange's mobile venture EE for £12.5 billion. BT had also held talks with O2.
Pay-TV provider Sky struck a deal with O2 in January to resell its mobile service and offer bundled TV-mobile-broadband packages, while people familiar with the matter have said Vodafone Group is considering options.