Brett Evans
it sounds like you have a clay type of sub soil which means water doesn't penetrate easily and will tend to stay near the top of the grass causing standing water. Ideally you would want to turn over or remove the soil for confirmation of sub soil, dig down to find a more porous material and re-lay top soil onto this with a weed suppressant. Failing this if the water is in one area only you could put a land drain in this area.
