Jacqueline, Masona is correct, this sort of damp proofing is a costly and ineffective waste of money.
One thing many people forget about is proper ventilation, if the air bricks have become blocked and there is no way for the property to "air" itself, then condensation will accumulate and cause internal damp in walls.
This does not mean that you need a new damp course.
Before you go spending money on this, get into the house and check ALL the airbricks have free airflow.
You often find these have been papered over, or had cupboards built over them. You need to check from the outside, then try to locate the airbrick from within..not always as simple as it sounds.
If you have a digital camera, take a picture of each airbrick, a wide angle shot will do it, so you can refer to the picture on the camera when attempting to locate it inside.
It might also help to draw a basic line diagram of the house, one for ground and one for first floor, then you can also mark the locations on this to help.
One good indicator of this problem is if INTERNAL walls appear cold and damp.
Remember also that if there is a basement, or crawlspace beneath the floor, this too needs adequate ventilation or this will cause damp in this part of the house, and this will rot beams and floorboards from below.
If this turns out to be the problem, then go to a plant hire compnay and hire a dehumidifier for a couple of weeks to dry the place out..ideally you want one up and one downstairs.
