Here's a more modern reference, Mitch Steel's IPA book:
Use Burton-on-Trent water with 0.068 oz gypsum per gallon.
Pale Ale Malt 97%
Crystal Malt 3% (# not stated)
Invert Sugar 1.13 oz per gallon at whirpool.
Color 13.3 L
Use 1.28 qt/lb.
Mash 154 for 90, then raise to 162
Sparge with 165 water.
90 min boil with targeted 10% evaporation.
Add 45% Fuggle (4% AA), 20% Challenger (7.4% AA) at start of boil. 5 min before knockout, add 34.5% Northdown.
Cool to 61 and pitch Burton Union yeast (?) at rate of .5 oz per gallon. Allow temp to free rise to 68 over 5 days.
After primary, cool to 43 and hold for minimum of 3 days.
Rest talks about racking into cask and finings.
Recipe looks very close to yours with just longer mash.
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Member of the Metro South Homebrew League (Mash-Holes) - Weymouth, MA
Primary - Annie's Atomic Amber, Pumpkin Ale
Secondary - Empty
Kegged - Dortmunder Export
Bottled - California Common (2nd place, 2014 OSHC).