I would like to find some sort of keyboard which can simulate the sound of harpsychord, to accompany early music played on other instruments. I know that there is Roland's gorgeous digital harpsichord which costs approximately one thousand pounds, but this is not the class of instrument I am looking for - I would want something which costs fifty pounds and which you can hide away when you don't need it. Can somebody please recommend something like this to me?

You could buy one of the lower range Yamaha PSRs for about £80 and use the Haprsichord patch(es) on it if you're not that that fussy about a high quality sample/waveform. Try popping into a music shop and test a few out.