Magic maggots

[JustGetThroughTheDay]

I hate having to ask this but I need some help. Early hours of the morning when I'm getting ready for work I realise that the 'blossom' (I know! It was early in my defence) on the ground was actually maggots. Lots of them. On the patio. I hot bleached and swept them into the big drain and hot bleached that too. Check again when I get in from work and all is well. Then tonight when I go to do last lockup there are more on the patio. We have a dog but she poops on the grass and it's picked up every day. No other outside animals, no reason I can think of for this well spaced out crawlies. Anyone any ideas?

Is there anything dead lying about? Flies lay eggs in dead things, they hatch into maggots and then change into flies.
Or did you drag your wheelie bin over that spot on the way to put it out or bring it in again recently?

They really are gross.

Nothing dead that I can find. That was my first thought. Wheelie bins no where near.
Husband thinks they are coming out of the soil?

Maybe they're not maggots but some other kind of insect larvae? Don't know what though!