Does it have tough dark wiry stems? If it does it might be self-heal.

I have this and Ojibway93 is right, 'Prunella vulgaris' it seems to have medicinal value too. Godgle it! :)

In lawns, use a weedkiller such as a 2, 4-D-based herbicide to remove self-heal. Apply in cool, moist, calm conditions when there is least risk of accidentally damaging nearby garden plants.

Saw some for sale in the garden centre the other day...six quid a pot !!!!!!!!

yep its prunella [self-heal] and the white and pale pink forms are valued garden plants but £6!!!!!! certainly need to heal the hole in my purse at that price.

Gosh ! I could make a pretty penny from my front grass, then!

Thanks for all the comments, I seem to have a choice of buying weedkiller or having a lawn sale.