Hi , We have a near side fixed bed Abbey Freestyle 540 and it is a pain to make up the bed , kills my back fitting the undersheet, the bed is very comfortable when made up and we sleep like logs under the duvet, we secure the base sheet with elastic stretch clips, like suspender belts. I was looking on the Raskelf's web site and noticed they make and recommend a zipped polycotton sheet to go over their memory foam mattress. I thought this might be a good idea, just roll out the mattress lay out the duvet and hey there you go, no more strained back. My question is how much do these memory foam mattress's move on top the sprung one, my wife and myself, erm, move about a lot in the night and wondered how much the memory foam stays in place. thanks for any advice.