I <3 Mild. It's one of my favorite styles. Enough flavor to be satisfying, low enough alcohol that you can have 4-5 Imperial pints without having to drag yourself home by your lips.
Looks pretty good to me. In fact, I have but one concern. Steeping the Maris Otter isn't going to do anything. You're also not going to get the full effect of the brown malt without mashing. Me, I'd cut the Maris Otter and roll with that. You'll probably have to increase the DME slightly.
I like to keep my Milds simple, because commercially they are. Pale malt, one or two flavor/color grist ingredients, either a mash adjunct or kettle sugar. Hops to just on the malt side of balance.
If you're really interested in the style, check out the book in the Style Series. Though dated it's worth a read. Just ignore the recipes, because some of them are stupid.