French Drains - Cost etc.

[KentishMama]

Does anyone have a good idea of what it should cost to have French Drains installed around the perimeter of a house?

It's approx 50 m in total and the ground around the house is mostly paved or concrete under a thin layer of pebbles.

Many thanks in advance!

Well since you don't seem to get any answers I tell you how much ours costed, it might give you an idea.
We had less than 50m to do, but they had to dig to the base of our foundations and we have a basement. It costed 20K $ in Canada.