I actually initially ordered the wrong size. It's not them, it's me. Perhaps unaccepting of my dad-bod, or underestimating winter chub levels, I ordered 2 Large jumpers. The quality was great when they arrived, but they were a little snug, and the wife laughed me out the room (nice bodyshaming).
Anyway, the return process was a piece of cake, and I had emails with 2 really helpful staff members, who have sorted an exchange. Awesome service.