Ban banning things
If I were a criminal, I'd pop across to Europe somewhere, buy a multi-sim capable device and bring it back to the UK. Then setup shop as normal. I can't see how a ban is going to prevent that.
If maybe I got sea sick so didn't fancy taking a ferry to France, then I'd buy a raft of cheap Android phones, with one sim in each and setup my sim farm that way. One computer can happily connect to dozens of individual phones, so it really needn't be that difficult. Again, a ban doesn't seem to be useful.
Hell, I'm sure a suitably wily criminal could produce a side-loaded app for a phone which lets it be "remotely controlled" to send/receive texts/calls over the network. You don't even need to put them all in the same building - you could have them physically located all over the country in your teenage mules bedrooms, in the back room of your club and in the wife's underwear drawer. The 'controller' can be a couple of your henchmen and a computer safely ticked up in a house in Elbonia - far from the annoying jurisdiction of the UK. Again, the ban seems pointless.
Suffice to say, however they choose to operate, the criminal fraternity are infinitely more inventive and adaptable than any amount of the government. I predict this will be largely a pointless endeavour. Are our government ministers and their stooges in the departments really not able to see this sort of thing?
When I see these sorts of things, I'm always left wondering why does the government feel it *needs* to do these things. WIth so many other problems, why "die on this particular hill"? I'm sure money has its part to play, but even still, it seem weird to me.