If it looks bad after mowing, you are probably not mowing often enough and then cutting down too low. Try more frequent mowing, weekly, and raise the blades a notch.
I planted a lawn last august it seems very patchy in some areas the grass is brown at the base and has green shoots growing out of it. When sowing the seed i used Humber Palmers organo -mineral Fertilisers No 13 and used it again in April. In june i put some sulphate of ammonia on it. Lawn looks well until it is cut
Lawns often start off patchy and settle down when fed a few times, as the fertiliser evens up the quality of soil as regards nutrient content. Also grass tends to brown in dry weather.