I went to Marks and Spencer in Bath yesterday. They had a 3 for 2 offer on ladies' socks (excl. sale). At the till, the assistant said that the rabbit socks had come up at 19p so they weren't able to do the 3 for 2 sale. I chose pair of elephant socks to be my free pair and got another pair of rabbit socks also for 19p.
I believe these may have been an Easter special which they're now trying to sell off. They're not available online - in store only.
Here's the link to the socks showing that they're unavailable online.http://www.marksandspencer.com/fluffy-rabbit-ankle-socks/p/p22441195?&pdpredirect