County towns are the most quietly useful thing on this list. They are asked in nearly every British quiz that has a geography round, there are fewer than fifty that matter, and hardly anyone has learned them — which makes the return on an hour's work here higher than almost anywhere else in quiz preparation.
Why they are harder than capitals
Because the answer is often not the largest town. Warwickshire's county town is Warwick, not Birmingham. The pattern of county towns sharing a name with their county holds often enough to be a useful default and fails often enough to be a trap — Cumbria, Norfolk, Suffolk, Kent and Sussex all break it.
Two of them have a historic answer and a modern one, and it is worth knowing which is which. Lancashire's historic county town is Lancaster; the county is administered from Preston, which is the answer these questions take. Yorkshire's traditional county town is York, and North Yorkshire — the county that exists today — is run from Northallerton.
The other difficulty is that there are several answers to "what are the counties". Historic counties, ceremonial counties and administrative areas do not agree, and a question written from one will be marked from one. Where a quiz asks about traditional counties, the traditional answer is wanted, even where local government has since reorganised around it. Some counties have no county town at all: the metropolitan counties — Greater Manchester, Merseyside, West Yorkshire and the rest — were created in 1974 and had their county councils abolished in 1986, so a question asking for one is asking for something that does not exist.
What else gets asked
Alongside the towns: which county is the largest, the smallest, the most populous; which counties are landlocked; which border the most others; and the county nicknames and their emblems — the red rose, the white rose, the Yellowbellies. Rivers and their counties are a natural pairing and setters use it.
British places with a story attached get asked in the same round: Hadrian's Wall and where it actually runs, Doggerland — the land bridge under the North Sea — and the Eddystone lighthouse, which is the answer to more questions than its size suggests.
Broader geography is here, and world capitals — the same skill pointed outward — are here.