I have jsut had the same problem as a numebr of you by email stating returning an item under DSR, refund email comes without original P&P included and I now need to tell thme I expected the P&P refunded and I am entitled to it.
In my emial I am going to state that in not refunding it tehy are in breack of DSR, as I did notify them of my return in advance. I shall also tell them that should this happen again I will notify the relevant authorities, and I will! Each and every time.
I also have a concern that when you email them through the website there is not an option to receive a copy of your own email so the could claim not to have received it! Until you have a reply you have no evidence of notifying them! Naughty naughty!!
I shall keep you posted!!