This is what I tried last December, and last month I did a side-by-side tasting with the real McCoy (bottle, US) which I and an English friend who grew up on the stuff found to be pretty darn close or at the very least within the same ballpark, tastebuds being different as they are
All-grain recipe, 5 gallon batch size
OG 1.058-1.060, IBU ~30, SRM ~21 (deep dark ruby)
75% Optic Pale malt
10% Simpson Crystal 75L
5% Torrified Wheat
2% Black Patent
Mash @ 150-154F
Fuggles 4%AA 2oz @ 60min
Fuggles 0.5oz @ 15min
Yeast: 1469 West Yorkshire @ 62-65F
This was the first time I used Optic and I loved it. Fat and juicy malt. But any british pale will do. Torrified wheat can be omitted as I don't believe the real recipe uses it. I thought it may have added a nice creaminess but at this level it might just be suggestive.
The sugar I used was homemade invert sugar "No. 4" as described here http://www.unholymess.com/blog/beer-brewing-info/making-brewers-invert
I couldn't definitively pick out the dark fruit flavors of this sugar in the beer and my bottles of OP didn't have that "treacly" character I remember from bottles I had more than several years ago. I'm sure one could substitute black treacle here but I have no experience with that. From the link posted, I actually used the dilution method with blackstrap molasses, Brer Rabbit brand.
The Black Patent probably could be swapped with roasted barley, chocolate, etc. I tend to like black patent and don't find it acrid. Any of that black character did mellow out to where my brew and OP were pretty dang close in character. If you're afraid to use it in the mash, feel free to throw it in during the sparge to reduce its flavor. The real recipe probably uses a jet black brewers caramel instead.
I used Willamette instead of Fuggles and didn't suffer from the substitution. OP in the bottle doesn't have much hop character in it except to balance the sweetness. Feel free to dryhop with Fuggles if you'd like.
I went with the Yorkshire strain and felt it was superb in this capacity. I've had mixed success bottle-conditioning with this and other similar English yeasts. Definitely carb on the low end- though I found the OP a bit spritzy in the bottle. If I were to bottle again with this strain, I may consider not priming at all as I suspect it reawakens in the bottle.