Hi @Manon22 
Welcome to the forum!
I love the look of that set but know my boobs wouldn’t fill it so don’t own it. There are a couple of reviews from people between the sizes that say it fits on the larger size so you might be better getting the smaller option (but my opinion is based soley on the reviews.)
If you get and it doesnt fit, you can return it if the lables are in tact and you tried it on with knickers underneath. Certainly there are members on here who have returned lingerie, some buy two sizes with the intention of returning one.
This is the returns policy 
I know what I’ve stated above doesn’t correspond with the return policy on lingerie but you really can’t tell if it fits without trying it on just make sure you do have something under the pants.
I’m also going to include this post from @Kitty-Cat01 as maybe she can help you with her experience on the returns policy for lingerie.