I made this map a year or so ago, by superimposing two maps from Wikipedia. (If anyone wants I can dig the source maps.) Lancashire is that red "bubble" up north. Rhoticity is dying in the UK, and specially in England.
And while the feature alone is not a big deal, since it's preserved elsewhere, it's a sign that local varieties are dying - and those are pretty unique. They're likely being replaced with Southern Standard British, by a death of a thousand cuts.
This also shows that claims that "American English" is killing the local dialects are likely false, otherwise you'd see an increase of rhoticity there. The local dialects are dying but due to country-internal pressures, such as identity; not due to simple media exposure. (This is, sadly, a rather typical pattern)