I too have a problem with ants....Someone told me they don't like apple cider vinegar (which I love!) -When I have good reason to use this -I will post in here.
Also quoted to me was 'antbait' which you can get at B&Q -apparently they carry this back to the colony which wipes it out.

Ants don't eat plants, even cabbages - they're usually present on plants because there are aphids present, and they like the honeydew they produce. Treat for the aphids and the ants will go.
If you think there's a nest nearby, you can now buy a nematode solution for getting rid of ants, made by Nemesys, available from The Green Gardener, but I've never used it, don't know how good it is, nor do I know if you need to apply it directly to a nest.

If you can locate the ant nest boiling water is solution BUT as ants themselves do no harm in the garden I would let them be.