Shout Out UK reports

As well as better regulation, the other big advantage that legalisation has is taxation. The Institute for Social and Economic affairs at the University of Essex estimates that legalisation could provide extra tax revenues totalling between £400 million and £900 million. The same study claimed that coupled with savings from the law enforcement of prohibition, legalisation could boost the UK economy by an extra £2 billion a year, with other estimates claiming that it could be more. Sales of the herb could be paying for hospitals and healthcare; stoners could be funding schools or social care. The economic argument for legalisation has obviously been won. If anything, continued prohibition has only had a detrimental effect on one of the world’s largest economies.

Putting it bluntly: Legalising cannabis could give the UK an extra 2 billion

The following reports are from 2015, so a little long in the tooth, but as we haven’t referenced them before here’s the details

and many more references from UK & International media at the University of Essex page