I would look in at Morgan
they have an Aiwa Minidisc for 47 GBP, but I do not know if it has an mic input, the simplest sony NH 600 hasn´t, alternatively go for the Olympus DM 1 as it has a mic input and variable sensitivity:
http://www.morgancomputers.co.uk/shop/products2.asp?CategoryID=201&SubCategoryID=144
the usual mp3 player records in awful quality, and with glitches because of the harddisk, these Olympus´ are at least designed for voice recording, although not radio quality, but you would need pro equipment for that.