In Ireland you can move mobile provider and get your number ported across in about 30 minutes, with no hassle and minimum bellendery. Because operators were basically made to do so. None of this "Oh, you need to give us 30 days notice to end your contract and only at the end can you ask for a PAC, at which point we'll ignore the request for two weeks" nonsense that's the norm in the UK.
So I say, as a citizen of that fine Republic - if a country as small and generally legislatively useless as Ireland can manage it, there's no reason other than tactically-pocketed brown envelopes that the same couldn't be achieved in the UK.