Yes you should be getting more than this but is it possible to try a speed test using a wired connection? As this would be the most accurate reading of your broadband speed. I would recommend using http://www.speedtest.net/ if you haven't already as it's a very popular and accurate speed test site.
Thanks for getting back to me with this information. As you can see there's a significant difference with the wired and wireless connection speeds and depending on what time you run the speed test this can impact on the result whether it's peak/off peak etc.
I would recommend checking out the links above regarding your wireless signal strength as there could be many factors that are interfering with it and even changing the channels can make a big difference.