I really like the Warminster Floor Malted Maris Otter but I can’t say I’ve tried every other Brittish base for a comparison. I use it frequently for Milds, Porters, Stouts and a few pounds going in my lower gravity American Pale ales.
It is used almost exclusively in many of the “vermont” ipa’s like heady topper. Makes a great beer, though I haven’t tried it in a porter/stout/bitter.