There are tricks you can do to make a space seem larger than it really is. First, you have to declutter. Review all the stuff you have and clear out those that you no longer use and are only hogging more space.
Second, consider painting the walls white or other neutral colours. Let as much natural light to come through by being smart with your window treatments. You can also add floor standing lamps, pendant lamps, and other sources of supplemental lighting if your room doesn’t have enough windows or doesn’t get sunlight very much.
Lastly, add mirrors to create the illusion of a bigger space. You might also want to rethink your furniture and switch to those with reflective surfaces to bounce more light around.
Despite these tips, there’s only so much that a non-professional can do. If you intend to make a huge transformation, check out DesignbyDeborah.co.uk. They have the best interior designer in Berkshire and you can see some of their samples at their website.