I’d be inclined to stick to what you are feeding already, if the hogs like it, and your local wildlife hospital has recommended it. Unfortunately, putting out any food could attract unwanted visitors and pretty much anything we feed them isn’t as good for the hogs as the wild food they find themselves.
Perhaps, bear in mind for next year that, presumably, the hogs were managing ok on their own before you started feeding them. So feeding can be an extra ‘helping hand’ without completely replacing what they can find naturally.
I wouldn’t rely totally on the hedgehogs not being able to get into the pond because it is too steep, and make sure there is provision for them to get out, if they do manage to climb up there. (If you haven’t already). Some hedgehogs are incredibly good climbers, and I’ve heard before, people thinking that the hogs couldn’t get into a pond but they have.
I like the name ‘Surrey’ (musical fan?). I often give the hogs slightly descriptive names.