Keep trying. Fax Your MP are interested in doing a published table of which MPs responsd and which don't so there may be some comeback in the future.

But to get an MP to do something it's best if you are actually asking them to do soime specific thing, like forward your query on to a named department or that kind of stuff. The department has to reply to the MP, and then he'll send the reply on to you. It's chipping away at a rock face, but that's no reason not to do it. MPs don't necessarily do much in response to letters, but if they don't get them, that's their excuse for inaction. So take it away from them.