Caterpillars On Basil

This year my basil, which I grow lots of, to make pesto, is being attacked by caterpillars. I have found one or two quite big ones, but can't seem to find the smaller ones. Which means, by the time I find them, the damage is done.
Now, what puzzles me is, butterflies / moths usually lay their eggs only on certain host plants. How many UK native species will have basil, which is a Mediterranean herb, as it's host?