Hi Alan, You have a couple of options in creating a vegetable garden where there is presently turf. If you have access or are willing to hire a turf cutting machine this will cut the turf thinly, you can then either discard it, compost it or turn the turf upside down in situ and let the grass and nutrients go back into the soil. Or you could weed kill the area you wish to dig up, waiting for the grass to die right back before digging the soil over.Nothing wrong with the membrane system either but the turf cutter idea would be the quickest. Whichever way you decide to go remember that you only get out what you put in, in other words if you look after your plot feed it well with manure compost etc it will reward you with plenty.