[quote=@The Nexerus]
<Snipped quote by KnightShade>

Neither my local MP nor her strongest competitor (whom I voted for) have any power at all, because neither of them are members of the party that currently has a majority in the House of Commons. Even if I influenced my MP somehow by writing them, they wouldn't be able to do anything on my behalf.
[/quote]

Opposition can have an important role to play in setting the political agenda or keeping the majority party in check. But, yeah I can see how, writing to a candidate you don't agree with, to put forward views they don't agree with, so they can present them to a parliament who won't agree with them, could be a huge waste of time.