Depends really on how basic and how cheap.
You could spend less than £20 on something if it's just for basic audio. Probably something from Logitech will do the job. If you want something that will be offer a bit better sound quality for some music, then Creative T10 should offer better sound for about £35.
Creative T20 are a noticeably better speaker than the T10, but they're more expensive now I've noticed. T20's used to be £55 and were certainly worth the extra; but are now £70. Maybe you would consider £70 a little too much, if the speakers are intended for just basic audio use.
If you're looking to spend less than £35, then it's case of pick something within budget that gets good user reviews.