http://wiki.homebrewersassociation.org/SSMinnowMildAle-AllGrain sounds good -- although I don't have brown malt (or biscuit or amber) - could I use cara red?
personally i wouldn't skip the brown malt, you need the contrast to the sweet flavors. any grain that has a bit of a bite to it will work, brown, chocolate, biscuit, amber (very good), etc. But if you can't get your hands on a grain like that, toast your own brown malt using pale malt. fyi, mild ale malt is good with the maris otter too, but all maris otter is fine.
<edit> IMO a touch of black malt is critical to fantastic dark mild ale, it's been included in every dark mild I've ever brewed and I should have included it in my list of "grains with a bit of bite." I can think of more than one big name
home brewers who will state that black malt has no place in a mild ale, history shows otherwise. cheers to brewingrover for posting a recipe that includes black malt.