Welcome to the Forum! Rats are one of the perrennial problems, unfortunately.
It sounds a bit worrying that the council put rat bait down under your workshop. I hope they put them in proper bait boxes and at a time when hoglets weren’t around.
Rats don’t tend to like cat food as much as some of the hedgehog foods, so you could try that, although you might encourage the neighbourhood cats instead. (I have found that if I ever have a rat around the cats seem to be mysteriously absent!) It’s easier to stop the cats getting at the food than rats, because you can put it in boxes with appropriately deterring entrances.
Other than that, keep a check around your garden for any rat bolt holes and fill them in. Sometimes you will get a particularly persistent rat who will keep digging them out again, but bricks, or something they can’t dig through might help.
You could also, only leave food out for the hedgehogs whilst you are around to watch. That way you can scare the rats away from the food. (rats are much more sensitive to movement than hogs are, so it’s easier than it sounds). This way also has the benefit that you can get to know your hog visitors better and observe some of their behaviour. Hogs soon get to know what time to turn up for food, if it’s only around at that time.
If you feed birds as well, you might find that what they drop is what’s initially attracting the rats. If that is the case, I can give you some other tips re. alternative ways of bird feeding.