Hello Les,
Assuming that you have been continuing to receive your previous PIP award that sounds as if they have decided to increase it and have given you a back dated payment, probably until last October.
It seems as if they trigger any change in payment at the same time as they send the letter out, so generally the payment hits a bank account a couple of days before the letter. Keep looking out for that brown envelople which should be with you in a couple of days. If you can't wait that long, you can always ring the DWP.
Catherine
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
