I wasn't aware of this til a week after it came in, so it might have passed one or two others by -
The small parcel rate size bands have changed as of 28th Oct. The existing basic rate of 45cm x 35cm x 8cm remains, but the previous 'exception' band of 16cm square has been upped to 35cm x 25cm x 16cm.
In a nutshell, TWO different small parcel size bands (technically 'small parcel wide option' and 'small parcel deep option'), BOTH with an up to 2kg limit. Both for £2.60.
Big improvement.