Laying a new lawn on a previously mature garden

I wonder if anyone can help. I have recently moved into a property that has a garden about 10m sq. It was heavily overgrown with large shrubs and and numerous climbing plants around the entire perimeter, some well established. I have a young family that require a fairly large lawn area and at the moment there isnt any. I have removed the majority of it but I am now left with a large area of my garden that is very rooty. Short of removing every root (nigh on impossible) can any one suggest how I should prepare the ground prior to turfing. I dont want to be faced with the old garden growing back through the lawn within the year !

any advise would be of help.

I have considered laying some form of geotextile down then 150mm of top soil prior to turfing but I a concern the soil will block the poreS of the geotextile and the lawn will not drain correctly

thanks

Gavin

 

that should work fine Gavin

 

I was really after an alternative method. I am concerned the soil will block the pores of the geotextile membrane and prevent the lawn from draining.
thanks