Hi, I don't agree with the advice you've been given. Yes in a perfect world that's the way the job should happen but you can get away with laying the new turf straight down so long as you break up the existing turf. You can do this by hiring in a lawn Airator(not sure of spelling) which should be "slit tine". go over the existing lawn with this in every direction you can think of which will break up the turf enough for you to lay the new stuff. Well water the new lawn for at least 4wks (don't flood it though) and hey presto, you've got a new lawn. Treat any weeds that grow through with "Verdone" follow the instructions on the bottle.