UPDATE (19th Jan): Price back up to £31! Good while it lasted!
Just noticed (12th Jan 2016, 10:30am) the OSRAM E27 Lightify RGB bulb on Amazon is currently £15.50 (Prime too!). I’ve got two of these already (@ £30 each!) so I’m getting a couple more - bargain! Works perfectly in ST (apart from the switching itself on once in a blue moon problem).
(Note - link above includes my Amazon affiliate code)