I tried a deep fried mars bar in Edinburgh while wandering down the Royal mile, but neither my friend nor I were particularly impressed - it tasted like cardboard.
A chippy in Buxton does deep fried Cadburys Creme Eggs at Easter. Which is pretty much as gloriously disgusting as you might expect, especially since the egg comes out covered in a gnarled knot of batter - it looks like something you'd stumble across in a Alien film...