No need, there's enough armed back up support and a F/A is a hindrance in most confrontational situations (rolling around on the floor with a drunk bloke who would then have an opportunity to seize a handgun).
More use of tazer is coming, all Boroughs in the Met now have officers trained to use tazer(until recently it was only ARV's and the TSG). Tazer is far more effective as a day to day tool than a gun.
For the record, I have been a cop for 22 years - I am not corrupt, inept and take a great personal and professional pride in doing my job to help the public. I have never in 22 years given out a speeding ticket or sent 9 cops to arrest a shop lifting Granny. Dixon of dock Green was a fictional character and those days did not exist, I personally would not want to go back to so called golden days when (although I have no proof of this whatsoever because it was all decades before I was born) it was common place to lock you up for 3-4 days in a cell until you put your hands up to something, where you could routinely be given a good beating because there was no regulation on what the police did and how they went about doing it.
Would I want to armed - no way as I don't feel arming all cops is a necessary or sensible path to go down.