When thinking of furniture cardboard does not spring to mind as the most obvious material to use. Children all play with boxes making hideouts at some point but it is not something that would be thought of for full size or permanent use.
Yale undergrad, Zach Rothholz built a chair that could transform into a shelf or coffee table out of three ply cardboard for a senior project and was so impressed by the materials strength, ease of use and lightness that he ended up designing a wide range of furniture, running a kickstarter and opening a store in Connecticut in the US. The store and the associated site are called Chairgami.
His range of furniture is quite impressive and while not as cheap as you would think it can be is not that expensive either. It includes, chairs, desks, sofas, tables, storage solutions, hamster wheels and even a bed. Particularly inspiring is his standing desk (which he kickstarted) – this has the huge advantage of being able to be adjusted to your exact ergonomically correct height and is very reasonable in price compared to a standard standing desk.
Also mentioned on the site is the use of cardboard as a way to effectively modify and adapt current equipment. The specific example is of a wheelchair desk but the possibilities are obvious.
At the moment Chairgami does not seem to ship to the UK, although they have promised that it is upcoming in a couple of places. You could purchase (or find) the cardboard sheets yourself and if you choose to do this it is sensible to also look at the method used by Rothholz – build small scale versions first!