Best Bitter

This is the recipe for the best bitter I am going to brew this weekend.
For 10.5 gallons, 80% efficiency.
15 lbs. Marris Otter
1 lbs. Munich Malt
1.5 lbs. Crystal 60 L
1.5 oz Challenger (7.5% AA) at 60 min.
1 oz. Challenger (7.5% AA) at 30 min.
1 oz. Challenger (7.5% AA) at 5 min.
2 Whirlfloc tabs at 15 min.
2 packets Safale S-04
og 1.050
Going to try and mash at 149-150 for an hour.
I'll post more after the session.