Ridding of weed/nettles/unwanted plants at end of garden?

hi. at the back of my garden there a 7ft by 2ft (ish) bit of land that is covered in fast growing nettles, weeds, and other things id rather not be there. what would be the best way to get rid of them all so that i could possibly get to the point of where i can turf it or put grass seed down to tidy it up? thanks...

 

hi, iv treated it with sbk brushwood killer yesterday. done exactly as it states in the instructions. today the nettles and brambles are wilting. how long do you think it will take for them to die? or should i do a second treatment? if so, when? thank you