To quote The Tao Te Ching:
The more laws you have, the more criminals you have.
Legalise it, standardise it (as in get rid of that horrible soap bar, even though I do smoke that if nothing else is around), and tax it. Think of the revenues the governments are missing out on.
It's long been proposed that the police are wasting their time chasing the users.
And cannabis used to be one of the major crops for Britain (being a naval nation and needing lots of rope, hemp=good rope).
See Britain could once again be great, a new economic revival based on hemp production.