Police in the UK are prohibited from taking any form of industrial action - so the Federation does not have the ability to create disruption (to forcibly get their way) in the way Police Unions in North America can (and frequently do).
The Federation represents officers up to Chief Inspector, the Association of Police Superintendents represents more senior officers, but below Chief Officer rank.
ACPO is for Chief Police Officers and is quite different. You should not conflate that as serving the same purpose at the Federation of AsPS.
British police officers might be prohibited from taking industrial action, but in 2004 many firearms officers protested by refusing to carry out their usual duties:
http://news.bbc.co.uk/1/hi/england/london/3973261.stm
The Federation represents officers up to Chief Inspector, the Association of Police Superintendents represents more senior officers, but below Chief Officer rank.
ACPO is for Chief Police Officers and is quite different. You should not conflate that as serving the same purpose at the Federation of AsPS.