I went to the Post Office today to send some crocs through the post, second class - normally £2.60.
However, it is now (second-class) £5.20 to send this item. It was 2mm thicker than the new width allowances (even though it was incredibly light 330g).
The PO worker told me these were the new rates from 2 April 2013. They have a new measuring plastic thing to check measurements for small and medium packets.
So, apart from buying/selling books (which counts as a small packet), that's it for me.