I have a concrete area around 150 square metres that I want to turn
into a flat lawn for the kids. My house was a farm so the whole area
around the house is solid concrete. The area I want to transform has a
brick wall surrounding 3 sides of it. The area is kind of cut out of a
sloped grass field - On one side of the wall is raised grass sloping
down towards the area and the other side is a slope down away from the
area also grass.

A major factor is I live in Fermanagh in Northern Ireland - a VERY
WET area, with poor drainage and clay soil.

I want the grass to be useable in the winter when it is most likely to
be waterlogged, so drainage is a major factor.

Should I dig up the concrete and remove it or break it up and use it as
drainage under some top soil? The project is going to be very
expensive so I want to get it right

Any advice would be appreciated