How do I get rid of mushrooms in my lawn???

How was the soil for the lawn prepared? Could it contain a lot of organic material or old pieces of branches or old roots etc? this might be the case if you have laid your lawn in an old vegetable garden.
The fungi are growing on something organic in the soil, but as this source is exhausted you should have no further problems (though it could take some time.)
I suppose you could spray with a fungicide, but if the lawn is fairly dry the fungi shouldn't be a problem.
Is the land well-drained?

When you say you've had a lawn laid, does that mean you got someone else to do the work? Because if so, they should come back and treat for the fungi growth. The fungi would have been present in the turf when it was laid. They should, however, eventually disappear.

Hi Bertie

The lawn was lay for us as this is a rented house. Top soil was laid befor the grass but the soil below was full of roots and alsorts. The garden seems to drain quite well.

We are having quite a lot of rain on the Fylde at the moment, but I am sure when everything drys the fungi will hopefully disappear.

Not sure what the top soil was like before the lawn was laid. Guess I will have to wait and see if the source gets exhausted.

Thanks for your comments and advise. as you probably guessed I am no gardener

Thanks Bamboo and Bertie for your advise. I guess it is just a waiting game