not as much as you might imagine. they are Mediterranean plants and their silvery leaf helps them cope in the hot Mediterranean sun.

I do my pots when its hot like this about every 3 days. the ones in the ground I don't water at all.

Seaburn girl thank you for your reply. I'm in Somerset, near Pilton, Glastonbury. We have had hot weather...its all rather unexpected.

I agree I dont water mine.

Unfortunately, we get it a great deal hotter than you do in the UK and for longer, and I don't think I have EVER watered my numerous lavender plants except when they were tiny cuttings - don't ever be tempted to feed them, either. They are very happy with maximum amounts of neglect.