Thought I'd post this because I had a hard time finding any I could walk in and buy, and Amazon damaged them in the post, so in case anyone has been struggling to find these.
Wilko have Growarm 100's in stock currently for £14.
http://www.wilko.com/propagators/sankey-propagator-electric-38cm/invt/0445580
Wilko have Growarm 100's in stock currently for £14.
http://www.wilko.com/propagators/sankey-propagator-electric-38cm/invt/0445580