On Thu, 14 Jan 2010 19:35:17 -0000, "Roger Mills"
wrote:

I'd just try it. If it doesn't work for any reason, you can always
over-paint it with the 'proper' stuff.

Thanks everyone. I had a reply from International Paints saying the
two were very similar but they had not tried chalk on the matt black
paint, so like you, they suggested try a small area and see.

They did also say the blackboard paint was specially formulated to
hold chalk on the surface, as other posters have said.

I will let you know what happens, when I get round to it.