periodic tenancy notice in writing??

Hi , my landlord is trying to hold us to a 2 month notice period which was in our original signed contract on 27/09/08. Since then we have not signed any agreement, so i take it we are in a periodic agreement and the 2 month notice no longer applies.
I telephoned him on the 27/10/12 to give notice, and since then he has made me sign a letter to say that i spoke to him on that day giving notice, but am still tied in.
My question is, does this new signed letter i have constitute "written notice" and should i hold back paying him the money he is demanding by the 28/11/12.
Thanks.