There was a proposal from Ed Vaizey in 2011/12
Mandation of the PSB to emit HD only on all Platforms
conversion co-timed withe the frequency change fir 700 MHz clearance
but as the minister I don’t think that the political reaction would have been that popular !
Sadly the temporary muxes have not met their objectives
So I feel that the current migration to SFN in the middle of the mobile band is a waste of government money which could be better employed by making the existing (PSB) muxes emit more efficiently .
There are many public policy / commercial effects if reducing the number of PSB mux to
(18 nations / regional and say 6 national ones ...)
like who will pay arqiva to broadcast nothing !
And who are the two mux operators