Welcome to the forum, @mattylad ; .
Jetpack by Wordpress.com may have the functionality that you are looking for but just like any other automated social media posting tools, you will not be able to post your content directly to Google+ because they have not publicly release their API for developers.
Tools and plugins aside, it's a pain in the a** to post your content manually to every social network, especially if you are the only person running the show. However, you have to understand that different users on different social networks have different preferences when it comes to content that they like to see or feel like interacting with.
For example, Facebook and Google+ users love clicking on and interacting with visually appealing posts (gorgeous images - manually attached or via Open Graph) while you can have your content stand out on Twitter by tweeting a quote from an article instead of the title itself which everybody else is doing.
With the above in mind, it is advisable that once you have the time or once you see quality visits coming in from either of the networks that you have been autoposting to, spend time crafting dedicated content or updates just for them.