I am experiencing problems with my rear parking sensors on my skoda superb and i wanted to know how to get to each sensor. i.e. does the bumper need to come off or just the black trim around the bumper?

I reckon you need to get this moved to the Skoda Superb section. Also since there are two versions of the superb you will probably need to give the year or Mark 1/Mark 2 so people know what exact model you've got. Working sensors should make clicking noise if you listen to them while they're turned on.