The answer to that question on the UK part is yes there are maps but they are pretty meaningless and approximate. You can't equate USDA zones to an island climate in my honest opinion.
Here's a detailed winter temperature map for the UK and S. Ireland BUT it's not following USDA zones and is more accurate than any other I've seen before. We don't have zones here, too many variables in our climate for that and the map is still approximate. I don't know who did this map but it's not a standard government thing. http://www.hardyexotics.co.uk/hardyexotics/frameset.htm
I have just joined Dave's Garden, and wanted to know what zone I am in. I found the following page which give the European hardiness guidelines, with the USA zones, and the Royal Horticultural Society zones of hardiness. Hope this is of help. http://www.seedsite.co.uk/hardiness.html
As far as I know there isn't an online USDA zone map for Japan. I understand from a friend who lives in Japan that it can be from zones 4/5 to 10/11, although, as I indicated above, these climate zones don't really help where you cannot be sure of the weather.
I would guess you're 10 or 11 as well, but since the USDA zones are based on lowest winter temperature if you know your typical minimum temperature in winter you can figure out for sure: Zone 10a has low temp of 30 (F), 10b is 35, and 11 is 40.
Does your temperature at night in the winter ever go below 40 degrees F? If it doesn't then you're in zone 11. If you occasionally get below 40 but not lower than 35, then you're in 10b. Or you can go to this page http://davesgarden.com/zone/ and Dave's got a link to a site that has some zone maps for areas outside of North America. Not sure if they have the West Indies or not but it's worth looking.