Skims review: Product/service I'm complaining about not being able to return goods

i bought Skims on line in the sales and having read the sizing reviews sized up to a medium when i am a size small. the items arrived and are huge which are not fit for purpose as they will hang off me being a size 10 UK.
i have tried the return process only to be advised that sale items cannot be returned. i am deeply upset as i paid nearly £90.00 for the set, i wouldnt mind if they offered size return but not to refund £90.00 is really not fair.
i have contacted trading standards and i am in my rights to return an items that are not fit for the purpose.