We brought a 2000 pocket sprung mattress on a double divan sprung base from a well known retailer. It was delivered on 8th March and the mattress has now sunk to a depth of approx 4-5 centimeteres where we lay. These dips do not go, leaving a lump along the middle. We are not heavy, myself being only 8st and my husband 12st. The dips are very visible even when the bed is made. We have complained to the retailer, but they are refusing to do anything about it. Incidently the mattress has been turned regularly. Should this happen to an expensive bed and a supposedly good make?

I previously had a 1200 pocket sprung mattress that was still good after 15 years with no sign of dipping. I would appreciate an opinion from an expert on mattresses Many thanks. .