Recorders are dirt cheap. Pick one up for £5 at any music shop.

Don't know about the Argos 1/2 size guitar, but I've got the 3/4 size for my wife and it's not too bad. Obviously not top quality, but good enough for learning on. Or go to a local guitar shop and look around.

Make sure you get a classical guitar (nylon strings, wider flat neck) to learn on. Steel-strung guitars have a narrower curved neck which is easier to play, but you get into bad habits with that, and then it's harder to learn how to do it properly!

Re the plastic instruments note, there was an article in the paper a little while back about a manufacturing student at some English uni who'd worked out how to make plastic guitars (and by implication, other stringed instruments). The problem is getting a light-weight front which'll still resonate properly, so he's invented something which puts little bubbles in to get a foamy kind of structure. Apparently the guitar isn't as good as a proper one, but it should be OK for learning on, and being mass-produced it'll be nice and cheap. Have to wait and see what happens with that.

Grab.