Duo Boots Trieste

I am so fed up with Duo Boots, I measured my calf and ordered the exact size, when they arrived they were huge on the calf and really snug on he ankle. So I ordered (after telephoning them) a different model in 8cm smaller - I could not do it up at all...so depressing... They charge £5 delivery even though the boots are expensive and you also have to £5 pay to send them back...I have now tried 4 different boots and the postage prevents me from trying more...maybe they should do an exact diagram with measurements of each boot - not just a general measurement for all models...