If the maggots had orange heads and were curled up in a shape like a comma, then they were vine weevil grubs. You need to water your compost witrh Provado Vine weevil killer according to the instructions on the packet. Or when the soil is warm enough, use the Nematodes sold to kill Vine weevil grubs. Sadly there is no organic way of keeping the adult egg laying beasts out of anything!

if they arent very very tiny maggots then they could be the dreaded vine weevil,if so you need to squash them,sounds a bit harsh but they are a nightmare.you can get a solution to pour onto the compost to kill vine weevil but it works out expensive.hopefully someone else can give you a clue if the maggots aren't vine weevil

If you have a robin in your garden he will soon find them if you leave them on a bird table or the path......recycycling. Check that he eaten them....if not...then squash them. I have been going through some of my pots and found a few. Later they change shape and get the start of legs and then become black beetles. The bigger pots will get a Provado drench

They thrive in peat based compost - so change it to non-peat based compost. Job done.