We just use a double fitted sheet which is for a deep mattress. I lift up the far side of the mattress (window side) to put on the fitted sheet, whilst kneeling on the 'near side', then drop it back, stretch the sheet across and fit the other pillow end corner, then tuck the sheet well under the 'cut off' corner - and it all fits like a glove, and never moves. We have a cheap polyster duvet overlying the mattress, but under the bottom sheet, which is why we need a sheet for the deeper mattress. We then have a four seasons down and feather duvet (two which velcro together to give differing TOG ratings) in a normal double cover - and we use the appropriate one, or both together, depending on the weather. In France, occasionally, we just sleep inside the duvet cover, with no duvet inside it, if it's particularly hot. I tend to tuck the duvet under the 'cut off' corner, which helps it stay put, and makes it look neat, too. During the day we often do what the continentals so, and throw the duvet and cover outside to 'air', or if not then I make up the bed neatly, and tuck the duvet under the corner during the day and it all looks neat and shipshape.