Clay and Ground Covers

I have a lot of clay at the bottom of my garden and I have some 'Mind your own business' growing. It's green small leaved, small in hight and will spread. Be carefull though, it will spread.
I like it but once you have it it will keep appearing and you would have problems getting rid of it.

How about trying Helianthemums? They love the sun and might thrive in clay... Worth a try as when they are happy, they make lovely big colourful (and evergreen) mounds.