If you live near a large city such as London, Birmingham or Bristol it's well worth keeping your eye on the local free papers to see if there are any folding bikes for sale. Quite often someone has decided that a folding cycle is the best way for them to commute to work, so they have gone out and bought the best folding bike 2012 has to offer, but then something has happened to stop them using it anymore. It's not uncommon for people to take a massive dislike to riding in the rain or maybe there job changes so that they work at home more. In this case they will often decide to sell it through the free small ads in their local paper. I've seen very good looking Brompton folding bikes for sale for less than £600, which is a bargain. Sometimes you will find someone who has decided to upgrade their Dahon folding bike to an ultra lightweight Brompton P6R-X and you can grab a bargain.
It's always good to support your local bike shop, but they tend to stock non folding mountain and road bikes more than folding bikes. Here are some places where you can buy new and used folding bikes:
Evans Cycles is a website and a chain of shops with a long history. The first shop was called F.W. Evans on Kennington Road in South East London. The shop established itself as a quality bike shop and also built it's own bike frames. After 50 years of operating at Kennington Road the site of the shop was re-developed and was relocated to Waterloo at 77- 79 The Cut, where the shop is today and continues to be one of the most well known bike shops in London. As well as the London shop there are now over 40 shops throughout the UK. The chances are that they will have a shop near you, but if not you can use their website and benefit from free delivery in the UK.
Evans tend to concentrate on the more quality end of the market, selling bikes they have confidence in such as Tern, Montague and of course Brompton folding bikes. For some reason they don't seem to stock the Dahon folding bike. Their website is really good and you can find some good user input there too. If you are in the market for a new bike, I can't think of any reason to go anywhere else!
Yes it's not just books anymore, Amazon UK have a massive range of folding bikes for sale which includes the Dahon folding bike range, the cheaper folding bikes by Raleigh and less popular cheaper ones like the Stowabike Folding City Compact Bike (which is only about £130). As you would expect from Amazon it is also a great place to find a folding bikes review, written by real customers.
Amazon don't sell Bromptons but oddly enough they do sell the pedals (both right non folding and the left folding ones) and few other spare parts and the Brompton Bike Bag, the B Bag.
Ebay is the best place to get cheap folding bikes as we have discussed before. By using the Advanced Search try looking for spelling mistakes and oddly worded auctions to try and get a bargain. You can also use the location search to find a Brompton local to you. Quite often the sellers ar quite happy to meet you at a train station so you can avoid any expensive delivery costs.
Halfords is a good place to quickly get your hands on an Apollo or Raleigh folding bike. Keep an eye out for end of season bargains (usually in September and October)
Argos won't really let you look at the products before you get them home, but like Halfords it's a good place to pick up a bargain. Sometimes you can get a few reduced items at Argos, just before the new catalogue comes out.