I have the same as Faskham - it is a little twiddly to get used to, but there's a satisfying feel to using it, as it's rather chunky, and it makes a nice whirring noise as it prints! £20 from WH Smith.
There seems to be two models of Letratag machines in the UK. My one has a QWERTY keyboard and is more of a "landscape" orientation (I think the ones previously mentioned were more of a "portrait" orientation). So far seems fine, you're not going to touch type on the keyboard though, far too imprecise for that.
I got mine in Rymans and I think it was about £20 too, cartridges about £4 each IIRC.
Font quality is fine for filing stuff ...
I even bought some yellow plastic tape so I could (finally) label all the plugs under my desk - stops me yanking out the CPU when I meant to undo the printer !!