As @Gnawme says, the term "US/UK" "appears in a comment to [a] BBC article". The comment as a whole is very badly written. As the comments on the BBC website are probably fairly transient, I am reproducing it below exactly as it stands:
At 13:18 16th Mar 2010, [name] wrote:
I hope this is the end of blind US/UK support for a state with a shocking record of
Lets remember that if israel gets away with this they are literally destroying any arab
hope of a capital in jerusalem. Therefor ripping apart any hope of a just peace.
They would also be breaking international law, and be liable, justly, to face international
its a disgrace that the US, above all, has turned a blind eye to the disregard of human
rights shown by israel for so long.
The lack of proper punctuation, capitalisation, etc. in the comment clearly indicates that the author is not bothered about correct formatting, etc.. Hence nothing can properly be adduced from any particular usage in that comment.
Having said that, I certainly was not aware that
The slash always means or (quote from comment by @tchrist above),
and I note that @Jacobm001 disagrees and states that
On the West Coast of the US, the slash has always indicated an "and or or"
I do not know whether there is a 'standard' British acceptance of its meaning, but I have always understood it to mean and or or (or some other alternative combinations when 3 or more items and 'linked' by slashes), with its exact meaning to be adduced from the context, or perhaps even left purposely vague.