I read somewhere that the sizing changed since they are no longer made in UK. Your best bet is to wear the type of socks you'd wear with them, go to the store in the afternoon/evening (when your feet are sightly larger than upon waking) and try on the exact type you want to buy.
Docs can be a headache. I bought three pairs, all within a year of each other back around 1989-90 and even though they had the same size number stamped on, they each fit differently. One pair was way too tight, another needed two pairs of hiking socks or my feet were swimming in them. The leather looked exactly the same; only the color was different and one pair had the rainbow stitching.
I also hated how they broke in. But I do still think they look cool and they were nice smelling boots when new, fwtw.