Comment by IshKebab

I've written to mine several times and usually I get a stock reply vaguely relating to the subject, but occasionally I've got actual replies. Once I sent a message about ordnance survey open data and they sent a clearly custom reply and forwarded my message to someone else.

In any case, my sister used to work in an MP's office and even when you get auto replies they tally it, and weight it quite heavily as a representation of constituents' views (unless it's a template letter in which case it goes straight in the bin).

It definitely has more effect than signing a petition - most of them are super dumb (lower taxes!) and as far as I know not a single one has actually changed the government's position. It's just too easy to sign them and too many dumb people do it.