After the complaint someone was sent out with the tools of the trade to check the mattress. Their response is that this was an acceptable amount of SAGGING. I absolutely disagree and we have purchased a new mattress from a different supplier.
Compaint placed a year ago;
King size, Rest Assured - St Andrews (20yr warranty), tempered pocketed springs. Even though the mattress is regularly turned correctly it is already sagging in the individual sleeping areas, which on purchase we mentioned we wanted to avoid, purchased 25 January 2011.