I just tried it today and it turn our great! I did modify your recipe slightly because my brew supply place didn't have liquid Maris Otter. Here is what I used.
3 lb Maris Otter Crisp (grains)
1 lb Caramel/Crystal 80L (grains)
12 oz Pale Chocolate (grains)
8 oz Black (grains)
5 lb Pale Malt LME...