Depends how much topsoil put put on - if you can see the blades of grass sticking up through a thin layer, then fine, otherwise, level off with topsoil to the depth necessary and sow grass seed - more than you think you need to let the birds eat some of it...

The alternative is to carefully remove the turf from the areas that need levelling, add the top soil and then replace the turf. It's more work but saves the need for re-seeding.

spot on ian,but i also add htat the top soil be compact an the turef slight proud

To true Derekf. That way when everything settles it will all be level again!