I think it still obviously depends on body shape. I started as a good size 18. Since lost a stone but still need 18 trousers but can fit in 14/16 tops. I have really big hips though so I know I'm always going to be buying bigger.
My retail therapy nightmare saga...my size 16 jeans are way too big and I am using a belt to hold them up, so went to buy new ones, couldn't get the size 16's above my knees, and I went to three different shops in my local designer outlet village. So, my tip is don't go on dress sizes cos all shops are different and you may become discouraged.
Incidentally after trying on the jeans I then tried on a skirt and it was so tight it was indecent. Not wanting to give up on some retail therapy went and purchased a new mobile phone, when I got home realised it had already been used and I couldn't put my original sim card in without paying £15 extra!!!
What a day!