In reply to lone:
Turn the bike upside down, resting on the handlebars and seat. Stand astride the bike and pedal with your hands, trying to push downwards with both hands as you pedal. This willl load the bottom bracket without putting load into either the chainrings or the rear wheel (which can also be a source of clicking). If the BB has gone, you should be able to feel it (i.e. if it's not silky smooth).
I've had this problem with a crappy old bike and a super cheap BB.
I've also had clicks from a) a chainring bolt which had worked loose and b) a loose rear spoke which rubbed against another under slight wheel distortion. Both gave once-per-rev clicks ( rather than click-clunks).