Salut everyone.

Over the last autumn I cleared an area of ground that was once a vegetable garden but had stood abandoned for over 10 years. I cleared it with a DR trimmer ( great piece of kit ) then rotovated it , treated it with weedkiller, waited 2 weeks then rotovated it again, and again. Then I put grass seed to create a lawn. I have been mowing it weekly since April. However the area is still infested with thistle, bramble and nettle pushing up through the new grass.
Any suggestions for getting rid of these pestilential weeds without killing off the grass ?
The lawn is 40 meters x 20 meters.

Cordialement