What is this we have growing over everything? It's now in the lawn.
is there any easy way to get rid of it?
It's called Mind-your-own-business or baby's tears, Soleirolia soleirolii (syn. Helxine soleirolii) .
Advice on dealing with it here http://www.gardenersworld.com/how-to/solve-problems/mind-your-own-business/
I unwittingly introduced this to my rockery years ago ; I wish I hadn't .