I'm posting this in Padded Cell as the Home Theatre occupants will probably be aware of this.
Ofcom are changing UHF TV channel frequencies to free up the 700MHz band (Channels 50 to 60) for the development of future
mobile services. They are moving multiplexes (channel groups) now located between 50 & 60 to somewhere between channels 21 & 48. Also some channels currently in the 21 to 48 area might be changed.
The first of these changes starts in some regions on 7th Feb & continues through Feb, March, April & May & depending on region more than one retune date is planned. The work will continue depending on region in Jul-Dec 2018 Jan-Jun 2019 Jul-Dec 2019 Jan-Jun 2020. Your local press should publish the detail, or your TV will tell you.
It might not affect you other than the need to retune, especially so if you have a wideband (group W or T) aerial. But if you have a narrow band aerial and/or you're in a fringe reception area, then you might need to get a new aerial. In a few locations you might need to have your aerial realigned to another transmitter; again your local press will have that info. The pic shows the various aerial groups, you can ID your aerial group by the colour of the plastic bung in the ends of the centre arm.
www services like digitaluk.co.uk/coveragechecker & others have useful info. Look at 700MHz clearance.