It looks like Lichens we had when we had a lawn have a look at the link
http://www.lawnsmith.co.uk/novice/pests-diseases-of-lawns/lichens-liverworts

Lichen or algae, or both - mosskiller will deal with the problem immediately, but lichens particularly are usually only a problem on neglected lawns, that is, those which are never scarified, aerated or fed and have become compacted, so if that describes your lawn, then the problem will recur periodically without remedial maintenance work on the grass.

Thank you for your reply. I am guilty of not never scarified, aerated or feeding my lawn this year. I just mow/cut it. I´ll get some treatment to help rid it. I first thought they were mushroom.

Cheers

Paul