Posted: 31/01/2014 at 15:44
I would do as already said and plant the herbs in pots, I have sage, thyme and oregano in pots so I know it works.
I would search Google and gardening books for herbaceous perennials that don't mind heavy soil. When it's dry enough then dig in plenty of compost and rotted manure. My veggie garden was clay and after years of digging in rotted horse manure it's now more loam than clay.