They've got plenty.
What makes you think they've got plenty?
One policeman has been shot dead in the last 7 years, afaik (in the US, it's around 50 every year). Around 60 people were murdered with a gun in Britain last year, around 10,000 in the US.
Guns were used in 4% of British robberies last year, they were used in 40% of US robberies.
That suggests US criminals have plenty of guns, it's doesn't suggest that for Britain.
Beetle, what's the reasoning behind the Bobby on the beat not being armed?
There's always been a feeling that as the criminals rarely carried guns, there wasn't a need.
It's worth noting that 11 of the 52 police officers murdered in the US last year were killed with their own guns. I'm fairly sure if the British police were fully armed, you'd have a similar situation, with more policemen being killed with their own guns than are being killed now when they are unarmed.