More than €1.75 billion has been pledged to improve the Orange and T-Mobile networks over the next three years.
Their owner, Everything Everywhere, which was formed by the two brands' merger in 2010, has promised to roll out superfast 4G technology to allow its UK customers to download music and films to their phones at office computer speeds.
The company has trialled the new technology in and around St Newlyn East in Cornwall, and it will bid for coverage in auctions later this year.
Everything Everywhere recently posted pre-tax profits of €1.66 billion - up 12 percent - thanks to increased demand for iPhone and BlackBerry smartphones.
CEO Olaf Swantee said it has benefited from a general switch to higher-revenue deals, with 48 percent of all customers now on contracts. Its customer base increased by 72,000 in the final quarter of last year.