The recipe does not specify which kit to use.
I've thought about doing this recipe, never got around to it yet... maybe for Christmas next year. I've looked around to try and find which kit other people have made it with, but without much success. I reckon if/when I make it I'll use the Real Ale kit, as I imagine it is not too strong in flavour to overpower the added spices, but will also give it a bit more colour when coupled with the amber malt which I would prefer for a Christmas beer. It's probably also a safe choice as it's reasonably mid-range of the Coopers kits in terms of colour and bitterness. These are however just my thoughts, so don't trust my pure speculation