Can anyone recommend a fast acting, kill everything weedkiller? We want to clear our overgrown garden (about 1-3' high at moment) which is currently a mixture of thorns, grass, weeds, shrubs and sprouting bulbs and create a rubber chip play area for the kids & a bit of new lawn. I used B&Q's fast acting weedkiller 4 days ago but it's hardly done anything, just singed the tops and smaller weeds.