I think the vast majority of the UK public accept that some officers around high profile targets need to be armed.
As the threat is more sophisticated with terrorism, acceptance of higher powered weapons in addition to automatic pistols, is understandable.
What they don't want are the whole force armed, the ones that have to be, to have been highly trained in the use of firearms.
Now if there was a truly massive upsurge in gun crime, that would be a different matter, however look at the response in London to an increase in drug related gun crime in the past 5 years mostly from Jamaican 'Yardies', more ARVs (all British Police forces have standing 'Armed Response Vehicles', mobile patrols with pistols/MP-5s, to quickly respond to any firearms incident), but also a massive intelligence led policing effort, (operation 'Trident') with community related work, which it seems finally paid off in the last year, as the rate of these crimes dropped quite sharply with plenty of arrests and weapon seizures.
Smaller scale operations in other cities have followed a similar pattern, however most Police do wear body armour, but that is designed as much for stab protection as for firearm protection.
Pepper spray is becoming more common with forces, and nitesticks have long since replaced the older wooden batons.
Baton rounds, used in Norten Ireland for riot control and available for UK forces, are starting to be used for dealing with some incidents, as a 'non-lethal' option of disarming someone, with either knives or a gun, a gunman last year in a domestic house seige was disarmed in this manner.
Armed police have always been at LHR
, but they were behind the scenes until the Rome and Vienna airport attacks in 1985, when MP
-5 armed officers started patrolling in the open in greater numbers.
Nuclear facilities have long had more covert cover from a small dedicated police unit, the red police vehicles you may see in London are from the Diplomatic Protection Unit, securing the many embassies/consulates, they too have always been armed.
The Ministry Of Defence Police are also more 'armed' than the average force.
Last year, the MoD police became more heavily armed than usual, as they protected ships carrying nuclear material from Japan for reprocessing in the UK, with SA
-80 rifles and the operation of 30mm naval cannon fitted to these ships as part of an effort to make them more secure against terrorist attack.
After a number of mistaken shootings in the 1980's, detectives stopped being able to draw firearms when required, (as epitomised in the 1970's fictional series about the London Flying Squad, 'The Sweeney'), instead they would be supported in future by an increase in specialist armed officers as required.
During WW2, police in some areas like London and the SE
of England, were able to draw pistols if they were happy with the idea of being armed.
This carried on, quietly, into the late 1940's, probably due to a temporary upsurge in gun crime, with all those souvenir weapons coming back with the troops from the war, some of which, inevitably, fell into the wrong hands.
Of course the most constantly armed police unit, for the longest period, are the close protection detectives of Special Branch, who guard senior politicians and heads of state.
A rather different situation in Northern Ireland, but the Royal Ulster Constablary, (now the Police Service of Northern Ireland), before the 'Troubles' started in 1969, were not all armed, but armed RUC officers were a more common sight.
In 1970, the RUC reserves, (the hated 'B Specials', a very sectarian group with a bad reputation) were disbanded, (causing riots in the 'Loyalist' community), this group, a law unto themselves, incredibly had been allowed to not only draw firearms, but to keep them at home as they were part time officers.
Loyalist estates had been full of homes with revolvers, Enfield rifles and sub machine guns!
However, as the RUC was reformed, they took on a more heavily and overt armed role, as part of the policy of 'police primacy' from the mid 1970s, allowing troop reductions.
Heavily armed RUC officers became the norm, though that has rolled back some since the ceasefire by the major terrorist groups.
You could say that the general unarmed nature of the UK police is about image, which it is, however this image is part of the policy of consent based policing, which affects in a positive way the interaction with the public, who would regard seeing all officers armed as a very negative reflection on the state of law and order and society in general.
Despite the occasional lurid headlines, the UK is generally, an unarmed society, the view of the police is that keeping as few firearms in circulation as possible, reduces the level of armed crime.
Historic experience bears this out, like the temporary upsurge after WW2.
Armed crime is still rare, the biggest problem is from illegal imports and illegal reactivation.
The fact that there is criminal money to be made with the risky (from both safety and the chances of being caught) reactivation of deactivated weapons, shows that 'proper' firearms are not still that easy to get hold of, despite urban myths about being able to get a gun 'from a bloke in the pub' etc.
Also, if you are involved in illegally dealing with firearms, you are looking at a lengthy prison sentence if caught.