The link above takes you to the webpages of The Guardian, where they review 10 British brewpubs (well at least one is a brewery tap, not a brewpub).   Amazingly for the British media they aren't all in London!   I'm quite chuffed to think that I've visited 3 of them & they were all great.

Read the comments beneath the article for more brewpubs that might be closer to you.   In particular; The Marble Arch in Manchesterⁱ, The Three Tuns in Shropshireⁱ, The Woolpack in Cumbria & The Kirkstile Inn also in Cumbria.

My no.1 would be without a doubt The Wasdale Head Inn, Wasdale, Cumbria.   Its a bit far from London - heck its a bit far from most of Cumbria - which means it remains relatively low key.   Its the best pub setting I've ever been to at the top of Wast Water, great pub layout & great beer.