Yes I took 12 GCSEs, but I don't class it as particularly rare since I went to a standard state school where over 30 out of 350 students took 12 GCSEs. I don't know of anybody who will be taking 7 A-levels, but there is talk that somone at my college last year achieved 8 A's at A-level. I believe this was possible since it included General Studies, and 3 maths A-levels. Apparently, the first 6 units are Maths, second 6 are Further Maths, and third 6 are "Additional Further Maths." According to most textbooks there are 25 possible modules, so this seems a possibility.
I would say that you have to count triple award science as 3 GCSEs because it is possible to get different grades in all 3 of them, but I am somewhat biased having done it myself.