I got a nice stainless set from Facom - I needed stainless because I bought it specially for diving, but it was under £20 if I recall correctly.
I find Facom pretty good make in any case and fairly priced by and large. I do also have a buttock clenchingly expensive facom T-bar set of allen keys, which is great and I'm glad I've got but it was close to £80; worth it, but still ...
I concur - I've got a couple of Bondhus fold up keys, useful as an adjunct to a set like that above. I think you can get a triple set of meteic, imperial and torx fold up or loose sets for quite reasonable money.
Thanks for the replies so far. I have an Aldi and a Screwfix (among others) nearby. I have previously bought Aldi tools, but while they may be cheap, they are probably not the level of quality I'm after.
I have some rather nice Facom t handled hex keys that I bought individually for the most common sizes, to cover everything else I have a set of Teng's. To be honest on a bike, you probably don't need the highest of quality, but I would stay away from the really cheap, made of cheese ones and also try and avoid using a ball end if you can help it.