I would also go for 12 months, declaring lower mileage. Ive just insured my 600 fully comp (including commuting) for £90 with only 3 years no claims. Declared 6k miles a year. Go on comparison site, choose cheapest, don't bother with legal cover etc. Also play around with security. Mine was cheaper NOT declaring any chains or locks, than it was to declare a disc lock. It's all a game; I think they assume you are in a risky area if you say that you use a lock and chain, hence premium is higher. And as far as I'm aware it's very difficult to get less than 12 month policy, you can pay monthly at a higher rate but you're just getting the 12 month rate on credit effectively.
just a note, they are getting more crafty with the policies now. On mine there was no option to state where the bike is stored when not at my house, and the policy states that if nicked further than 300metres from my locked garage, the excess is doubled.