The majority of the keys on your keyboard should
match the ST layout, I believe. If you're talking about country-specific issues (e.g. the £ sign is missing, or # si in the wrong place), then these are largely down to the country version of the TOS image you use.
There are plenty of images on google of different ST keyboards. Unseen Menace (from this forum) produced an image with the UK layout on it here http://www.atari-wiki.com/?title=Atari_ST_Scancode_diagram_by_Unseen_Menace
. If you compare it to a US layout, you'll see there's not much difference.