Treat with a liquid mosskiller applied by can, or wait another 2 weeks and apply a Lawn Feed, Weed and Mosskiller granular preparation. It may also help to aerate the lawn if the soil is heavy, or its not been done for some years. Rake out the moss once its blackened, and reseed where necessary.

Moss is a sign of damp, so you will need to aerate it. I would rake it with an ordinary garden rake then fork all over it. Then through sandy compost over the aerated lawn then throw over some grass seed. It will look awful but will look fine by end April. Personally I would not try mosskiller till after raking it - Bamboo is correct though as normally it just comes back over time unless you improve and aerate the lawn.

thanks for that lots to think about and do, i'll let you know how I get on