I don't follow this phrase:
"...while only 37 per cent of primary sets are using Freeview the vast majority of the remaining 1.27 TVs are reliant on free-to-air digital TV which is vulnerable to 4G interference..."
There is no broadcast terrestrial TV in the UK except Freeview now, and it is essentially the same thing as "free-to-air digital TV " unless satellite (Freesat) is being considered, which won't be susceptible to 4G.
I suspect that what is meant is that 37% of TVs have built-in Freeview, and the rest rely on separate Freeview boxes, in which case all will be equally (in)vulnerable to the problem.
It will be interesting to see the outcome of the experiment, though.