Jancis Robinson is a wine writer that is fair and honest on most subjects and her thoughts on the quality of English wine seem about right to me - there is great potential, some people are making world class wines but not everybody is there yet. The link above was her view after a tasting which caused lots of feather ruffling in the English wine making community particularly because she wasn't very positive about still wines - she tells it as she sees it! She questions whether the quality is sufficent for the price and style. My view is that there is a niche for them just in the way that conumers happily pay £7-11.00 for Albarino, Gruner Veltlinger or even Picpoul which is now pretty fashionable in London restaurants despite being very very neutral. For me the varietal Bachus could hold the same place for England and Wales, interesting flavours which would be difficult to repicate in another country.
The point is, when people buy things like Champagne, quality is not actually the priority. Just as it is virtually impossible to tell one lager from another or one brand of cigarette from another, this is also true of Champagne. The famous names frequently buy finished bottles from cooperatives and stick their own labels on. Quality has to be up to a certain level but image is what counts. Having worked the West End of London as a Champagne rep in the 1990's , the brand managers really couldn't care if messages about dosage, malo lactic or reserve wines were getting out. It was - who is drinking it, where are they drinking it and who can we tell?