So, its freeview that look after the transmitters/channel use etc these days?
Arqiva look after the transmitters under contract(s) to the various Broadcaster(s).
Once every 4 years there is possibly something actually worth tolerating terrestrial TV for
In
your opinion. Many would disagree. BTW most, if not all, terrestrial channels are also transmitted from satellite.
and some idiot thought it was a great idea to use this period to mess around with the allocation of DTV channels, particularly HD.
Eh?
Digital UK | Clearance events in 2018 indicates NO transmitter works for the 700MHz clearance since June and none until Wimbledon is over.
Both World Cup and Wimbledon - while of little/no interest to me personally - are considered highly important by the Broadcasters... hence they usually veto any works (except emergency) to the Broadcast infrastructure during such events. (Imposing a technical lock down.)
Unusually (although maybe 'cos it is a fairly trivial change? I'm no longer privvy to such details) Channel 5's owners have replaced 5Spike+1 on Freeview LCN 57 with Paramount Network Channel today 4th July...
That may require a rescan or add channels type of retune if you want the new channnel.
It is possible to ignore such prompts until it is convenient to do so. MY TV has yet to nudge me to to do so (but did warn me about my transmitter's 17th July retune).
The current high pressure weather systems
are causing interference from distant transmitters that is outwith the Broadcasters direct control to some locations. So that may mean when you retuned you missed the HD mux?
Where are you located (roughly) and what transmitter are you watching? What, exactly, is the problem you have and want to resolve?