Ah, I often think about this subject as I own quite a few ukxxxxxxx.com names. For example I have ukholidaycottages.com (doing nothing with it at the moment)
holidaycottages (co.uk) goes to quite a nice little site that just sells cottage holidays in the south west of england.
to me, having the uk at the front of this one describes the whole area and of course people from overseas might look for the .com before the .co.uk (assuming that the americans know that we use holiday not vacation!!) Luckily in the UK we mix and match between .co.uk and .com. I am in Australia at the moment and everyone uses .com.au (which has made me think a lot more about ccTLDs)
If i was looking for holiday cottages in the uk, my dot com version is what i would type into google? I think it also depends upon what is actually happening at the .co.uk site. If some some company got lucky and just have their little site there, then it may be safe to presume that they wont go nationwide?
Also generally I prefer the UK to be at the front of the term with the generic in a plural form.
richie