This is mentioned in the anti-fascism forum but I think there is some use in it being here too.

All of the following are first hand accounts of involvement in British militant anti-fascism, great reads, entertaining and informative:

No Retreat - Book on AFA during the 80s and 90s, beginning with the inspiration for its formation in 1979. Brilliant.

Anti-fascist - Great author, again, entertaining no nonsense account of militant anti-fascism, from an anarchist perspective this time.

The 43 Group - Similar vein as the other two, but from a different era.

You can get these from Amazon or Freedom Books.