Ordinary or extra bitters shine using MO.
Try 90% MO, 10% Simpson's medium crystal, 24 IBU of EKG at 40 minutes, 6 IBU of EKG at 15 min, W1968 (London ESB) yeast. I carb this one on the low side similar to a real ale. This went over really well at a local fest. If you can find it try Wyeast 1469/West Yorkshire. I like this one slightly better because it's definitely a maltier, fuller bodied beer.
Mark