I do feel for the officers - the lot of a Uk armed response officer is not a happy one - darned if you do, darned if you dont hardly covers it.
BUT - going purely from details as reported - we dont know if there is any background to this - the approach taken lacked the most critical element of tactical operations - a dollop of common sense! There are ways that this situation could have been explored short of a full on forced entry. But again, background not known - but without some fundamental indication of an immediate threat then purplexing response.
However, to harp on about my theme of the month - Hopolophobia

- it becomes a little less surprising when a society is led by the nose down the road of demonising an inanimate object ( or for that matter a group of people be they jews, muslims, black, white, catholic, mormon, shooters etc etc ). When the word 'handgun' is being forced to acquire the same connotation and self awareness of 'Witch' in 18th Century Salem. I know I'm being very boring about this - but all roads do lead back to this.
Back to the poor s#d with a Glock who is the first through the door of that bedroom. Assuming a lot as no background details, so for this example I'm going to claim his only background info is that the man had a big handgun and the woman was terrified. He enters the room and the man has the remote/ black long object in his hand and happens through pure shock reflex to turn toward the officer with it. You have 0.2 of a second to react. Recipe for farce to become a tragedy for ALL concerned?
For all of those happy and content with our current lot on the front of firearms perception and legislation, you are ( respectfully ) living a dream my friends