Christian McArdle wrote:

But will the frequencies change during analogue switch off?

Yes, definitely. In most areas the three public-service muxes will move
on to three of the four original analogue channels. The other three
will go elsewhere, TBA. Channels 31-40 and 63-68 will no longer be used
for what is currently called Freeview, but might be used for new TV
services such as HD and/or DVB-H.

I'd still prefer to install a wideband in case they do.

This is a good strategy, although it's a fair bet that in large centres
of population (i.e. areas served by Crystal Palace, Sutton Coldfield and
Winter Hill) everything will remain more or less in the original aerial
group - although that won't necessarily apply to any new services.

--
Andy