I've done this for so many issues in the past and not once have I had anything more than an automated reply. Often those replies then go on and reference a totally different bill that I'm voicing an opinion on. This isn't all just one MP either, I've lived in many different areas of the UK in recent years and most of them have flipped parties at some point or another.

Maybe this is the "Westminster Bubble" the journo's keep talking about. Whatever it is, MP's seem very reluctant to interact with their constituents unless they're campaigning for re-election. At that point they'll turn up on your door step in the middle of the day, expecting a half hour conversation.

How is a citizen meant to adovcate and voice their opinions when their representivies, and every candidate looking to replace them, refuses to engage?

This isn't really a specific question, or a critism on your point. It's just venting on my experience in recent years. Maybe someone else has had a more positive experience they'd be interested in sharing?