Robert,
From my experience we have set our targeting to UK and have as long as i can remember as we are a UK company, with a .co.uk website,
I think Google see's it as more of a guideline, as this targeting has never held us back internationally as roughly 60% of our traffic comes from worldwide and we rank well in the states particularly,
My advice is to go ahead and target UK especially if the website is only applicable to UK
Hope this helps
James