Would a double sheet fit my mattress?
I have a Sealy posturepedic mattress measuring 135 (width) by 190 (length) by 29 (width) cm. I need to buy some sheets for it and am currently looking at Argos but I’m not sure if what they have will fit my mattress since I’ve already bought a double mattress protector from them and it barely wraps around the bottom edge of the mattress… I think mine must be a bit deeper than standard double mattresses because of the extra foam. So what kind of sheets should I buy? Flat or fitted? Double or maybe something bigger like king? If you don’t know the answer, would any of the sales assistant at an Argos store be able to help?
@Jenny: Thanks for the answer, but does anyone know a UK company or store that sells sheets for extra deep mattresses? I assume that is a US one since everything’s in dollars.

ALL stores in the US that sell linens do. it’s almost impossible to find standard ones anymore. I’ll guess it’s the same over there. Have you bothered to look yet?
You have a double or full size mattress, but it seems to be extra deep. What you need to buy are fitted full size sheets for extra deep mattresses. Try looking here:
http://www.preciousbedding.com/extra-deep-pocket-sheets.php