The black patches are the dead moss after the treatment ? you need to rake that out. Also you must like me be in a drought and your lawn is dry? Wait until the weather turns and it should improve.

thank you , im panicking as iv entered my local garden comp and my garden will be being veiwed in 4 weeks so hope we"ve had rain by then and thank you again

Do you have the hosepipe ban? - every garden will be in a similar state if you do! Good luck