The best thing about brewing a mild is that you get to dial up pretty much all of your favorite malt flavors, in whatever ratio you’d like, in a session-strength beer – and all you need to do is back out the black barley and sub in a bunch of fun character malts. You can still have a touch of roast in there (if you want), but you also get biscuit, toffee, nut, molasses, toast, plum, raisin . . . you get the picture.
Bateman's XXXB Bitter won Gold in the Premium Bitter/Special Bitter/Strong Bitter category in 1986, 1987, 1988, 1989 and 1997. It is described as "A brilliant blend of malt, hops and fruit on the nose with a bitter bite over the top of a faintly banana maltiness that stays the course. A russet-tan brown classic." From this I would suggest a yeast that provides a fruity character. The data I have for this beer is: OG: 1.048–1.049. Malt bill: 72–87% Pipkin or Maris Otter pale malt, 7.5–12% crystal malt, 0–3% wheat flour, 15–18% invert sugar. Hops: Challenger, Goldings. IBU: 37. EBC: 40–42.