Interesting points, but I disagree: Criminals can and do call the police when crimes are committed against them. I accept they might not if they have a personal distaste for all law enforcement, or if it might lead to them being suspected of a crime, but I don't know how common either of these cases are. I admit that not having seen a handgun around where I live is poor evidence. A better indication would be how often people charged with crimes are found in possession of a firearm - which would inevitably lead to an easily provable additional charge. In my, (quite extensive), experience of criminal cases, I've only seen a handful of such charges.
As to the geopolitics and war on drugs, the UK is much more similar to the US in terms of the severity with which it pursues and prosecutes drugs offences than the rest of Europe. Its maritime borders are hard to police and drugs flow in from North Africa, the Middle East and more recently MDMA labs in India. However, you do rarely see the police in paramilitary gear (they use that for policing protests...) and I doubt they have access to tanks. This reinforces my point: when the legal side has regular access to weaponry, the other side acquires it too. When the legal side is not regularly armed, the need for criminals to arm themselves similarly diminishes.