[Stooky Bill]

A 'nightlight' style service on PSB1 isn't quite the same on DTT as it was on satellite. If they decide to close down SD they'll certainly put up captions but thats probably where the similarities end

With the satellite services 5 out of the 5 BBC transponders were converted to DVB-S2 and one left as DVB-S for backward compatibility. On DTT there's only 2 BBC multiplexes, one DVB-T and one T2 so there's nothing that can be done until it was closed. They can't mix the modulation standards in a multiplex - it's all or nothing. I suppose possibly HD on a T mux alongside SD is possible? Not desirable though

There's no advantage with de-regionalising, the only reason that was done on satellite was because everything was going onto one transponder. The coding and multiplexing kit for PSB1 exists already and is fairly new, I don't think there'd be any real advantage in reducing it's use.

If it happens (and AIUI there's no plans to) then they'll publicise it lots both in and off air, but you won't see a 'nightlight'