Got lots of this coming up... what is it?

[spandit]

Thought it might be ground elder, but the leaves are in pairs whereas with GE I think they come in threes...

 

[Muddypaws]

Looks like early sycamore leaves. Sycamore must have close to 100% germination rate, and it has a habit of taking over. Luckily at that stage of growth they should pull out quite easily.

 

[Mesquite]

Looks like early sycamore leaves.

Yup... I'd go with that ID

 

[spandit]

Thanks! Makes sense, there are a couple of sycamores close by. They'll get mown over if I ever get round to fixing the mower...