For cheap but pretty good liquid, I echo the statements made by others, vapour world uk per ml is probably the cheapest. Their stuff is Chinese though really, Dekang though, it's good quality I especially recommend Ry4 intense, let it steep though.
Paradise vapes is very good too, their banana creme is lovely and their caramel Ry4 is also a good mix. They also have a decent range of tobacco flavours, even if, some of them are hard to tell apart from each other to me... The drums very good as is their camel.
Moving to the not so cheap but still reasonable (especially since if you get 6 you get another 4 bottle free right now) is the Titan fluid from TW. It's still Chinese really, but it's good stuff, their Ry4 and RY3 are lovely juices. Strawberry, watermelon, tobacco and apple are not bad either.
Ecig wizard have some good (but expensive) exclusive juices, the only place I know of in the uk doing FSUSA mixes and pink spot liquids, you will pay a premium for them though.
ENjuice sell some of the best juices around, especially their dessert vapes. They have a value range which is quite well priced. Try the maple waffles for sheer buttery, syrupy loveliness.
IVapour have a small range of juices but do sell the superb Janty RY4 a juice quite frankly so good I'd pay whatever they charged for it! *
* well nearly.
