Verified answer

On Hunter's website at

http://www.hunter-boot.com/faqs

the following advice is given:

Do I need to order a size bigger than I take in a shoe?

No, we recommend that you purchase the same size as you take in a shoe as our boots do allow for wearing thicker socks.

I wear Hunter wellies for my daily "constitutional" walk along a muddy track. I've worn Hunter wellies for more than twenty years, with thick and thin socks, and I've found such advice to be sound. I've tried both sizing up and sizing down with Hunter boots over the years. When I tried a pair one size bigger than my normal shoe size, they felt unwieldy when I walked long distances in them. When I tried a pair one size smaller than my shoe size, they pinched a little in use. Hunter wellies in my shoe size just felt a little roomy with thin socks and a pair of simple insoles (available in different thicknesses) was quite effective in reducing the extra space.