It is expected that the auctioning of this band will raise significant revenue for the treasury as well as having a positive economic benefit by allowing mobile network operators (MNOs) access to increased spectrum allowing them to provide better data services. The 700MHz band has very good propagation properties (i.e. signals pass through walls etc well) which should improve mobile coverage in rural areas.
Digital Terrestrial Television (DTT) services will continue to operate in the 600MHz band, though multiplexes will use MPEG-4 and DVB-T2 technologies (any tuner that can decode Freeview HD will work with these technologies).
The main users affected by this will be Programming and Special Events (PMSE) radio microphones, who will have to move to other bands.
Whitespace technologies may also be affected, however these haven't really taken off in a big way and even Neul that has built equipment to utilise whitespace have recently concentrated on licensed spectrum (and have been purchased by Huawei).
This may seem daunting, but Ofcom is not proposing that these changes come into effect until 2020 (and maybe 2 years earlier in 2018), this is in-line with European harmonised spectrum strategy.