Virgin Media (NSDQ: VMED) will begin offering mobile broadband dongles in the UK in the final calendar quarter. Virgin is late to the UK’s booming broadband dongle space but today’s earnings reveal the offering comes after it struck an agreement with its MVNO backbone T-Mobile to reduce the wholesale rates it pays for voice and data, retroactive to January and April retrospectively. It will also lower mobile data tariffs accordingly. Virgin, which is also testing 100Mbps cable broadband in England, also committed today to introduce 50Mbps in the second half of the year. More earnings at PCUK…