you could try dry body brushing. you can get a dry body brush from the body shop for about a fiver (thats were mine was from but im sure they do them in loads of places like boots etc), before you have a shower brush your body in big strokes in the direction of your heart. this gets rid of loads of dead skin cells, the build up of which could be causing the spots. dry skin brushing is also good for circulation, the dreaded celluilite, and removing toxins from the skin. for spots on your bum try buffy the backside slayer from lush, its like a scrub in a bar, it works wonders.