Its a right pest !! mine is doing the same, I wait till it is looking brown in the early spring and scrape it off with a hand claw or fine rake, its an ongoing job I find ! and all you can do is keep at it! Ill watch this space to see if anyone has any idea,s

have you tryed verden

Yes try Verdone Extra.Ii've found it very effective on most weeds found in lawns. Far better than most granular weed and feeds. You may be a bit late to use it this season but once the grass is growing strongly in spring give it a go. So far it's killed even problem weeds in lawns I look after for customers

I agree, Verdone Extra is the biz!

thank you all for your interest and help.looks like i'll have to wait until next year to try it though