I am still on 3G, the provider keeps calling me and asking me to switch to their new plan. I just keep telling them that their current plan I am on is the world's best and there is no way I would switch to anything else.
Is the UK not going to sunset 2G? Here in the states the last 2G towers are disappearing here in a couple of months, and much of the network has been gone for years.
IIUC, 2G and 3G both require a fairly sizable block of spectrum to operate. If you have three carriers all operating minimum width 2G service, it adds up. 5G has some sort of coexistance story with 4G so in the future when LTE is being killed, they can let it live a bit and only waste spectrum as its used.