Hi @eoincurran,
If you want to monitor your voting power, you should try out https://www.steemnow.com where you can see your basic statistics in a simple form.

You can limit your voting power even if you don't have 500 SP but - as much as I know, only on mobile, using the eSteem app. It works on Android and Iphone. It is not perfect, but getting there.:)
In the settings you can set your voting power percentage which will be used for every vote you make through the app.