What would my average clothe size be if I was 9 and a half stone ?

Stone? What do you mean?

Stone is a measurement of how much you weigh,

9.5 stone = 133 pounds to us yanks. Are you male or female?

Oh I see now. Sorry to impose.

Knowing your gender and your height would help in answering this question.

15 5ft 7

A UK size 10 to 12 is my guess, but it really is only a guess.

Each country has different sizing systems. Sizes also vary between brands. I think the best way to determine your size would be to provide your measurements... or you can just go to a store and try some different sizes on! :)

... are you a woman? I found a link where a bunch of women discuss this same question, and many of the women who provided their sizes are more or less in your height and weight range. However, you'll also see that their sizes vary too. The pants you wear will also be influenced by your body shape or how you carry your weight.

This might help:
women 5'6" 135-140 pounds?