What will we do with 600MHz?
Local TV for local people ...
Handsets aren't quite that stupid; by default they assume they can attach to the same network they were last connected to, and failing that they'll check frequencies owned by the same operator (depending on the intelligence of the handset). However, the point is that scanning all those bands is complicated, and scanning a band where there's no international agreement on slots or technologies is next to impossible.
This means that any application for 600MHz isn't going to be mobile telephony, despite Everything Everywhere's optimistic suggestion that Ofcom sits on the frequency until some future date when it becomes harmonised.
We could use it for point-to-point connections, lightly licensed as 5.8GHz is currently. That would enable rural communities to link into internet connections over tens of miles with cheap kit, connecting up hundreds of not-spots without government-subsidised satellites or giving more money to BT. But that wouldn't fill the airwaves to capacity across the UK – which is Ofcom's primary remit (specifically "ensuring efficient use of radio spectrum", not "serving the interests of the biggest companies" despite how often the two things seem to overlap).
Ofcom had said that the consultation on 600MHz would be out by the end of March this year, though given the amount of effort the regulator had to put into the 4G proposals that's likely to have slipped more than a bit. When discussing the 4G auctions, the leader of Ofcom's Spectrum Policy group, Hyacinth "H" Nwana, suggested that the broadcast TV channels could end up being sold off as "there are players waiting" to buy them and broadcast TV has had its day.
But with such little interest or application for 600MHz it's hard to imagine who would be interested in buying the frequencies surrounding it, unless Ofcom knows something we don't. ®