UK police need more specialist firearms officers.
There is currently no need to arm all UK police officers as long as firearms support is there when it is needed. This is what polls of serving police officers have concluded on several occasions, and this is also current police policy.
If you arm all police officers, it is also almost certain that standards would drop. UK firearms officers are currently far more highly trained than armed officers in places like New York, and the only way to equip all UK cops with guns would be to drop standards (and increase accidental or illegal police shootings) or fire huge numbers of police.
The police federation and most forces in the UK are currently aiming to equip officers with tasers, which allow them to deal with weapons more safely but without the problems associated with giving all cops guns.