First point of reference is NO2ID's lobbying guide:
http://www.no2id.net/downloads/print/NO ... oLobby.pdf
Remember to establish what your MP actually thinks before berating him about the party line or his performance. If he has doubts about the scheme, or database government, then reinforce them. If he appears not to have, then find some fertile ground in his other concerns to sow those doubts. Remember he has a massive number of issues competing for his attention, and may just have missed some point that would be important to him.
(This doesn't mean he is stupid or idle: Read the list of 80 or so Acts of Parliament since the last general election, and ask yourself what you know about each of them. If you are still not convinced, read the hundreds of Early Day Motions, all of which someone will have approached him to sign.)