there seems to be an AFED chapter (east) kent but since their contact is a myspace i dont know how active they are; http://www.afed.org.uk/links.html
also there was some anti-fascist mobilization in Rochester last year against Britain first so probably there are some contacts there; http://antifascistnetwork.org/contact/
i would just contact the various nationwide anarchist and anti-fascist groups, tell them you want to become active (tell a bit about yourself so they dont think your a cop or fash) and ask if they can bring you into contact with local activists.
The mind is its own place, and in itself Can make a Heaven of Hell, a Hell of Heaven. What matter where, if I be still the same, And what I should be, all but less than he Whom thunder hath made greater?
Here at least We shall be free