@ Mike
But then there is no jurisdiction called England. For the purposes of law there is "England and Wales", which is of course a remnant of the old Kingdom of England (which included Wales) because the English and Scottish legal systems have never been unified. With regard to administration/jurisdiction though (and counties are units of such) then within what everyone understands to be England there is the United Kingdom and there are counties. Nothing in between. Which is not to say England should not be used of course -- it would be foolish not to when it suits --, only that, if you were to insist strictly on using only a jurisdiction, England would not fit that description.
Likewise America is a continent not a country (albeit, granted, we do use "America" now as a short-form alternative to USA). But the various pre-independence provinces and colonies there have a pretty clear history, so it'e easy enough to figure out which one to use.
It's a fascinating subject and I could cheerfully discuss it all at length, but the top-level field is not an issue. It's the muddle in the middle with places like Gloucester or the City of London I'm wondering about.
There is no absolute right answer, of course -- hence my sounding out other people here to see what their thoughts are.
@Adrian
The counties corporate were originally separate counties (in the sense of rights and privileges), but I believe a lot of that got gradually eroded over time with the poor laws and so on, until following the creation of the administrative counties in 1888 they were either made county boroughs (if they were to remain self-governing) or else merged administratively into the surrounding county while retaining their separate lieutenancies (= legal identities). In the administrative county of Gloucestershire, for example, I think the Lord Lieutenant was referred to as the "Lord Lieutenant of the County of Gloucestershire & The City and County of Gloucester & the City and County of Bristol", or some other mouthful along those lines.
The Royal Mail just confused things even more when they brought in "postal counties" (yes, they put Bristol in Somerset), but at the end of the day they were just routing instructions for mail distribution and nothing of import.
My
instinct would be to use the historic counties too, and it works well in rural areas or for towns in the middle of their counties. The problem with that though -- using Birmingham as the example with which I am most familiar -- is that as industrial cities on the edge of ancient counties grew and absorbed surrounding areas, their administrative counties were adjusted accordingly (as one would of course expect). Consequently, the ancient Saxon divisions are lost within these urban areas. When the only reference on documents is to the city, Birmingham, or to the administrative county, Warwickshire, then it can be very hard to determine whether a particular street was originally part of Warwickshire, Worcestershire, or Staffordshire because the original field, or hedgerow, or stream that marked the boundary was paved over 200 years ago. More than half of what we now consider Birmingham wasn't ever in Warwickshire until it was absorbed by the city (see
http://www.british-history.ac.uk/vch/warks/vol7/pp1-3).
Ironically, to my mind, the shires were first created by the Saxons to be rational administrative units and they adapted them as required to suit their needs. But because the government in the 19th century overlaid a new set of administrative units on top of the old, rather than just modernising the existing, we have the the confusion we have now. I got into a great discussion once with a staunch advocate of the historic counties, who felt Saxon administrative boundaries had to remain inviolate 1200 years later even when they clearly no longer served as any point of reference in urban areas that had "transferred" to another county a hundred years previously. Many people in Birmingham would readily agree that they were in Warwickshire, not the "West Midlands", but tell anyone living in the half of the city immediately south or east of what is now considered the city centre that they are in fact in north Worcestershire and they will look at you like you have gone soft in the head. Worcestershire, they will tell you, is a rural county and it starts 10 miles down the road on the other side of the Lickey Hills.