I think this is a great idea but would be a huge bit of work in itself given the huge range of dialects across Britain.Modern broadcasting and a more mobile population are watering things down quite a bit I think. Regional accents still exist but a lot of the regional "languages" - variations of English with their own words are dying out. Maybe some of it is also thanks to the move away from rural areas and agriculture to the cities as many of the words were specific to farming.In my own experience growing up in parts of Scotland I can see that Dorric (Aberdeenshire) and Norn (a Shetland Isles blend of English and old Norse) seem to be spoken far less now than when I was growing up (not that long ago!). The accents are still there but many of the words are slipping out of use. Comparing the way we speak today with the way my Shetlander grandparents (who were crofters) spoke for example is almost like comparing different languages.That's not to mention Gaelic, Welsh and Cornish.