Nowhere on that link can I see reference to it being the HP version that you are looking for.
There is a newer version out now.
Give Pacer Marine a call, not everything is on their website. I got my BST 12 HP Batt from there within the last year, for less than the price of the (non HP?) you linked to.
As I said earlier, inside that black box that is screwed to the base, is simply a 7ah gel battery which is simply connected to shortened version of the croc clip wires of the non battery version. For £20 and couple of spade connectors, you can convert non batt version to batt version.