You can buy a budget 32Gb from Play.com for just £18, while "quality" brands (Corsair, Sony) are around £50. Depends on how reliable you want it to be, and how fast you need it to read/write.
If you are going to use it as your vital backup drive, or you want to copy big files often, it's probably worth spending that bit more.
I can recommend Sony vaults - never had any probs and they are fast - but I also use cheapo sticks for some stuff.
Bear in mind that a £50 stick will probably cost £25 by the end of the year!