tedster - 7:48 pm on Oct 21, 2010 (gmt 0)
so google can pass on all the link value to the .co.uk for uk based ranking
It's a different domain, so that's not likely to happen this decade. A link to one domain is not going to pass juice to a different domain. To a company, it may all be one "online presence" but technically it is still a different website.
You've pointed out one advantage to using separate directories for separate countries, but hosting them all on one main domain. In that scenario you can have separate geo-targeting for separate directories.