The upgrade doesn’t seem easy, nor vastly more efficient. What data are you aware of that makes you say it will be easy? I’m reading that they’ll even need to put up more towers to get the same coverage because 5G frequencies won’t travel as far. Your finger-snap to 5G everywhere idea doesn’t seem to align with reality
I used to work for EE, so I know a thing or two about this kind of stuff, but I am not claiming to be a telecoms expert.
I previously stated that more base stations will be needed & a large number of existing 4G base stations can be easily upgraded to support 5G. It's not like the dark days of the 3G>4G infrastructure upgrade!
Most large cities in the UK should see a relatively fast roll-out of 5G. Of course the roll-out to smaller towns will take longer, but thanks to existing decent 4G infrastructure the roll-out will be be quick rather than gradual.