Here we've put together a some information to help pick which bicycle is the best for you, whether you're planning a grand expedition or just need something for popping to the shops.
Racer / Road bike
As the name suggests, these are designed for use exclusively on the road. They have very thin tyres and are usually very lightweight, however they are unsuitable for carrying kit and are far from designed for comfort. But if speed is what you're after, then this is the bike for you! Carectomy has a very helpful guide to buying a used road bike HERE.
Touring bikes combine some of the merits of road and hybrid bicycles with the practicality and hard wearing nature of hybrids. If you're going for a long trip then a tourer is exactly what you need. The CTC website has a good guide to Touring bikes HERE.
Hybrid bikes are considered by some to be something of a mongrel in the bicycle world. They're a jack of all trades and a master of none. With wider tyres, a sturdier frame and a few trimmings these are good for a general purpose hack on the road or a trail. Check out the CTC website for more info HERE.
Mountain bike / MTB
Mountain bikes are designed exclusively for off-road use. They generally have fork or full-frame suspension, very sturdy frames and knobbly tyres. They are completely unsuited for road use but really come into their own on rough terrain such as in forests or up mountains. CTC have a very good article about mountain bikes on their site HERE.
Recumbent bicycles are, as the name suggests, ridden riding in a lovely relaxed position. They look a lot like an armchair-on-wheels but aren't as silly as you might first think. As more of your body is in contact with the bicycle over a larger area there are less specific pressure points and therefore can be a lot more comfortable to ride than conventional bikes. On top of this, they are said to be 30% faster than a conventional bicycle. However to achieve this and get used to the new riding position you'll want to take about 6 to 8 weeks to practice before you do any serious rides. You can find more information about recumbents on WhyCycle.
Tandem bicycles are a great way to enjoy cycling with a friend, but at the same time it does involve spending extended periods of time with said friend! Tandems come in all shapes and sizes from touring to mountain biking. A benefit of having two riders rather than one is that you've got increased power downhill and on the flat, but it can be cumbersome going up again. However, they're not the best for just nipping down the shops or a quick ride. Having said all that, tandems can be a very personal taste so make sure to do some reading and give it a shot. WhyCycle have a good guide on their website HERE.
The FreeRadical bolt-on kit allows you to convert your bicycle to carry much mure stuff without too much effort. Have a look at their website HERE.