This is a fairly traditional action to take and might not be appropriate for every issue that crops up, but registering your concern over certain issues (or even praising them for good work) with your elected representative is what they are there for.
You can find out who your MP is and learn about the stance your MP takes on various issues here: www.theyworkforyou.com
You can write to them direct using this site: www.writetothem.com
If you want to go further and Lobby you MP on an issue, find some advice here: www.parliament.uk/get-involved/have-your-say/lobbying
Let us know how you get on!