The question was "are there regional QNHs?" - the answer is a simple "in the UK at least, yes".
However, unless you are flying a VFR nav at a particular altitude outside of controlled airspace then they have very little relevance to anyone. If you are VFR, any "altitude" info is purely for information, as you should get a "proper" QNH/QFE when you arrive at your destination airport.
If you are flying close enough to an airport that you need an accurate QNH, then in all honesty the ATIS will give something that is much more relevant.
In anycase, the variation in QNH over a region that covers about 5% of UK airspace isd likely to be pretty small. Also, a great deal of the traffic around is above the trans alt anyway (maybe you should aim to fly above the trans alt on 1013? Would that be a safer bet as everyone else up there is on the same setting?).
I can't remember what they do in the USA and Canada because of the 18,000' blanket trans alt - could someone remind me (it is 10 years since I last went there). i would have though that a regional QNH/RPS had more relevance there than in the UK.