Hi bga84
Like you, I never knew there were so many cats around – that was until I got night cams. Some of the cats here can get into just about anything, but interestingly they aren’t so keen on visiting when there are more hogs around.
Personally I would not use one of those cat deterrants with hogs around. Some people will tell you (possibly including those selling one to you) that they don’t bother hogs, but in the same way as rat deterrants they can’t really test them on hogs, so don’t really know. At one time I was using an ultrasonic rat detterant just during the day, but one evening it was accidentally still out when a hog arrived. I saw it visibly flinch when it went past. Needless to say it was hastily removed. So I wouldn’t want to risk using any ultrasonic deterrant with hogs around. Being night animals, they rely a lot on their senses of hearing and smell.
Hopefully your feeding station will deter the cats. A simple sheet of perspex type stuff on soil filled 2 or 3 litre flower pots will deter most cats, if it’s big enough and has the advantage that you can still watch the hogs. As said, there are sometimes one or two cats who are more determined than others!
Good luck and happy hog watching.