Like you teabagwoman I have heavy clay and when it's baked dry, it's like digging concrete. I was given an electric weed remover: a bit like double headed forked trowel that cuts through the soil and surrounding area, making it easy to grab the deeply bedded weeds and remove them. I can't say I'm that impressed with it though; if you're not precise where you put it, it simply chops the weed up and spreads it further. I now prefer to wait until immediately after a good shower of rain, when the soil is softer and more easily dug, and attack the weeds then.