Good luck. It seems this is not a very widely distributed brew outside of England. Its all I drink whenever I'm in England for business but I've never found it in the US.
I'm flying blind here as I have never had the beer in question. You could try starting with Jamil's Dark Mild (Brewing Classic Styles) and and tweaking it. He uses pale chocolate - switch that to normal chocolate. Maybe add a little brown malt (more of a tawny porter) and bump the gravity up to get 5%abv. Just some ideas. Hopefully once the holidays are over you get a better response on the UK forum.
Some of Jamil's recipes are on-line but I highly recommend his book. Check out his dark mild recipe (link). You could brew that while increasing the gravity. The recipe you linked to does have (IMHO) too much wheat.
The hops are Challenger and Goldings, and the abv is 5.2%. They also mention the presence of Cystal malts (duh) though not much else. Based on this I would imagine a simple grain bill consisting of MO and crystal 40.
Edit: Oops, I failed to notice Satanic Mills. The link I posted of course refers to the original bombardier.