That might be because some UK police refuse to carry because the UK doesn't have laws to protect officers (those laws that the US has that are constantly protested). https://www.theguardian.com/uk-news/2016/may/15/police-chief...
Can't say I blame them. Why would someone take on the chance of being charged with murder for carrying out their job's duties? It's not an easy problem to solve, but I think the ease of access to firearms is only going to increase, and they're going to have to get the UK police sorted with carrying.