Where can i get foam cubes cut to size near Cheshire?

Try telephoning an upholstery shop. They will have foam and may even be able to sell you a bunch of scrap pieces that you can glue together to make a cube. Depending on the size of the cube, you may have to make your size. Cutting foam is very easy if you have an electric knife, yes, the knife that is used to carve a turkey. Using rubber cement glue will be ideal to glue pieces together If you need to make a bigger cube, first, glue the pieces together, let them dry, then cut the cube to size after drawing lines with a straight edge and a felt tip marker.