When you say laurel, do you mean Aucuba japonica, Prunus lusitanica or P. laurocerasus or its smaller cousin, P. Otto Luyken, or Bay laurel (Laurus nobilis)?

I believe the plants in question are Bay laurel

Bay would be an unusual choice for a hedge, but a minimum of 6 feet, preferably more, given this plant's tendency to produce extra growth from the roots.

Thank you. I may have got the exact laurel wrong but our neighbour has planted them about 12 to 18ins behind the wall.

The worst would be if they're Prunus laurocerasus, the Cherry Laurel. google it to check - these get enormous if left to their own devices, 25 feet high, but they do have some pretty big roots.