I thought I'd treat myself to a pair. Prices range from £15 from Decathlon up to a whopping £85 for a pair of CU glasses. The middle ground seems to be covered by Y&Y who make a "Plasfun" version which you can get for £45 for navy blue, £55 for supa-fun Euro colours, or £65 quid for a pair of metal framed things.
Anyone used the Decathlon ones? Good enough? £30 extra is an awful lot to pay for a brand name.