You can get the BB614 fretless, I saw one in Hobgoblin Music (Birmingham) a few months ago for £175. If it was a better colour and not so roadworn i'd have had it, despite the fact I don't play fretless. Probably should have had it anyway and made a few quid on it's flippage.
EDIT: You can get TRBs fretless too, but certainly not under £500.