Not got around to brewing it yet myself but below is the meat of an email from Jason Oliver, the brewer who worked with Banks to create it. Hope it's of some use............
Below are some instructions I gave another UK homebrewer who used a 40L system a while back in regards to the DB American IPA that you're familiar with:
My main suggestion would be to up the amount of hops, below is literally a scaled down hopping of the beer. We brew it at Banks's and use their yeast strain. I recommend using something similar but if you use dry yeast, the Fermentis 04 would work well. The grist is simple with 96% Boort Pale Ale malt and 4% malted wheat. Any high grade of English pale ale malt would work well. Standard infusion mash. Banks's mashes very high (69C) so do what works best on your system. ABV is 5.2%, SG 1.052, IBU's 35 (although I speculate it's higher). It's dry hopped twice, once in primary fermentation and once in conditioning.
I broke the hops down into grams per liter then multiplied it by your 40L batch size. The first two hop additions will look low. In fact I think you should add anywhere between 15-20% more hop per each addition, perhaps more. Larger systems get better efficiency & hop utilization. Banks's gets almost full hop utilization with the 10 minute before boil end addition, you will not. So I recommend upping all additions. This is a linear scale down but it won't taste the same. Take it into consideration.
This is a scaled down hop charge by weight for 40L.
Kettle hops:
Admiral at first wort - 10g
Admiral at 10 minutes before boil end - 11g
Cascade in whirlpool - 34g
Centennial in whirlpool - 50g
Goldings - 13g
Columbus - 16g
Dry hop in FV:
Cascade - 5g
Centennial - 5g
Admiral - 13g
Goldings - 13g
Coumbus - 5g
Dry hop CT:
Cascade - 14g
Centennial - 8g
Columbus - 8g
Balance this with your knowledge about how your home system works. Hopefully you can do something with this. Once again this is a linear breakdown, I would up the hops quite a bit.
Cheers. Tom