Been missing the Digital Switchover? Good news! There is going to be another
I must admit that I have been occasionally called to task to when I posted here on UK Free TV some possible changes to the Freeview transmission frequencies for around 2018. It does rather seem as if this warning was as accurate as it was well intentioned.
The "700" band.
Going back to the May 2012, I introduced Ofcom channel bingo II - introducing the bands.
"These international developments are important because mobile spectrum needs to be used internationally to provide the economies of scale required to ensure a wide availability of devices at reasonable cost." … "EU states to … make the 700 MHz band available for mobile data use by no later than 2022" 
What does this mean for the viewer?
In the end, it should mean more-or-less the same Freeview service for most homes.
One thing is certain, and that is Ofcom "will not seek to ensure the continued delivery of the interim multiplex", so that will be the end of the extra Freeview HD services.
Because there will be a need to provide the same TV services in less broadcast frequencies there may be some knock-on effects. This MAY include moving the COM multiplexes to DVB-T2 transmission, so they will only work with Freeview HD boxes.
The change in frequencies may also need some homes to change their aerials (to wideband, if they don't have them) and very tiny number may need the "4G" filters.
Looking at the Arqiva indicative timescales 
It would seem that switchover events might take place in 2018.
Will this be the last change?
"The report also recommended that the 470 MHz -694 MHz band continue to be reserved for terrestrial broadcasting and PMSE until 2030" so it could be that there will be more changes in the coming decade.
What does this mean for the broadcasters?
The following diagram shows how the main Freeview masts operate.
The preferred plan that Ofcom has indicated is the Arqiva "Reduced Scope’ Solution (RSS) plan.
This will mean that some reduction in DTT power output levels will be acceptable whilst the services are moved to the reserve (in the sense of a "backup") outputs. Whilst the reserve is in use the primary systems will be change to operate on the new frequency allocations.
Once the national "clearance event" happens, the backup transmitters will be change to work on the new frequencies. The obvious issue here is that the DTT system will be running without a backup – at least from some masts for some time.
Keeping the backup systems in place would require the provision of up to 21 temporary masts. Given that the whole network of transmitters is still less than a decade old, it might be reasonable to think that the system will operate OK without the backups.