Just incase you haven't already found it, both the UK and US versions of their sites have nutritional information on their foods, but better still, on the food's components! Yep, you can view the carbs for the burger itself, the cheese slices they use, everything. So when you skip the bun from now on, you know exactly how many carbs are going in. Wish all fast food joints done that.

Mmm, i think i'll have a double whopper with cheese please....

For US people : http://www.burgerking.com/nutrition/components.htm

For UK people: http://www.burgerking.co.uk/the_facts/facts1.pdf

Enjoy!