So if you are doing 180 kt during circling approach you are still not in D category as , your Vref will still be in the C category when you cross the threshold
APPrOaCH category is for straight in and is based on Vref (vat 1.3vso or 1.23 vsr whichever is higher)
CIRCLING approach category has nothing to do with VREF (your aircraft aproach category), it is solely based on the SPEED you are going to fly it.