It's possible, but a rather skilled job if you want it to look and feel right afterwards. It also depends on how the foam base has deteriorated, sometimes the surface of the pad has gone powdery or the whole pad has softened. The foam base is also normally overlaid by a thin layer of scrim foam which comes in varying thicknesses density and qualities.
Bearing in mind the specialist skills and materials (and all the fiddly little clips!) I'd recommend either a professional car upholstery job or cheaper still will be a replacement seat from the breakers.
One advantage of a pro job though is that it won't really cost any extra to sort out the appallingly poor lumbar padding on the passenger seats fitted to a number of Rovers.