Need to raise it a bit since the gap between the body and bumper is a bit too big and to clear it from the tail pipe.

Is it just a matter of ondoing two bolts at the back and push it up or how is it secured? (it sits fine towards the rear wheels but look strange from behind with a gap of almost an inch)

/Andreas the mechanical retard

 

There are two bolts accessible from inside the boot where the bumper has two prongs that sit inside the chassis legs, have a play with these, or take the bumper off completely and investigate (it doesn't take long!) You may need to use some tape/wedges to raise it up slightly.