How come my bra size is so big but im clearly not as big as a topless model :S?

I'm a 32GG (uk size) in bras. I'm even spilling out of that a little! But everyone thinks that's huge! My bra off does look massive like my boyfriend takes the mick and can fit his head in one cup size lol, but people are really shocked when they find out what size I am because when you think of that size you think of jordan or jodie marsh etc- they look huuuge but apparently I'm the same size! I'm a uk size 10 usually, it depends though especially in tops as I have a very small waist and quite big hips so my wardrove can vary from size 8-14 in tops, but jeans I'm either 10/12. I'm 18 by the way.