The US does certainly have a "superior and mature setup for General Aviation than the UK", and 1-800-WXBRIEF is certainly part of that.
But, it is nonetheless much easier on most smaller British airfields to self brief, because that is what we are primarily expected to do, just as it is easier on most US airfields to contact the briefing service (for which there's no direct British equivalent) - because that is what we are expected to do there as our primary source of weather information.
Both work; if I had to choose between between the two I'd have the American one (albeit primarily for the ease of obtaining NOTAMs and the ability to file a flight plan at the same time), but I still like my charts - which are not so readily available on most US airfields.
I'm not US bashing, I hold licences in both countries, have had great flying in both, and have many friends in both - but there is a difference in the philosophies where some things are concerned. This is often for good reasons - weather patterns in Britain are often much more localised, whilst in the US it is much more important for safety reasons to provide mechanisms for internal traffic to file flight plans. For example!
G