Im afraid I'm with Met Police at the mo. Heres my two-pence worth - someone covered this partially earlier but i think they had a good point.
Wearing the POLITE jacket.... - not a big deal i feel. Most motorists will prob note it mentally an move on. Nearly all Met police cyclist will ride fairly assertively and ride "like they own the road" in the primary position is what one said to me [i dont cycle in the job]. i think if theres any learning to be had here, it'll be in the position on the road you adapt, not what is purported on anyones jacket that will keep you from harm. Would the guy wearing the jacket get stopped and spoken to? i would be surprised if they were..
Not everyone likes police - what if a slag who is anti-police is motoring behind you and decides to give you a close one? or your route to wherever takes you through a slag council estate? - would you not then be unwise to purport to be police when you are not?
Flashing blue light..... - could get you in trouble. We all know its regs to have white at the front and red at the rear. No where does the highway code state that blue lights are acceptable and should be used. Unlike the POLITE jacket which is more a passive statement, flashing blue lights are making a positive statement of 'emergency services coming through' which provokes an abnormal reaction in other motorists - which in turn may cause drivers to make unforced errors. would the guy with the flashing blue lights get stopped and spoken to? Probably yes - be given words of advice.
So, my [two-penny] conclusion - wear the jacket if you got one, but beware you may get what you ask for.. Dont use blue lights at all, its arrogant, illegal and it may erode the potency of it for people like me for when i might need it. There may come a time when you want those on blue to get to an incident without confusion and motorist wasting time trying to suss out its authenticity.
What would happen if everyone used a blue flashing light???????