I planted a raised garden bed a few months ago (trying to be organic) and got a few good months out of it, but recently the whole garden seems to be infected by these little flies and grubs. I seem to find them on the same plants so I think the grubs must be the larval stage of the fly but I'm not certain of that.

What I find is little holes all over the leaves, very small - but so many they always seem to be more hole than leaf. I'll then find some of the grubs on the back of the leaves (they're only a few millimeters long) and the flying bugs will fly up and around whenever I disturb them. If I don't pull out the plant when I find grubs, within a week or so the core of the plant will be covered in these little grubs. They started on my asian greens, and now all those have been ripped out they've moved onto the english spinach. Plants they haven't touched include celery, herbs, beetroot and kale.

I've ripped out half my garden trying to kill these things, and I'm reluctant to use chemicals without even knowing whether they'll work - so I'm wondering (actually desperately hoping!!!) If someone else can tell me what they might be. I've searched dozens of websites for what they might be but I can't seem to find them.

I have a photo of the flies if that helps - http://i1350.photobucket.com/albums/p764/spatchya/2013-07-09164025_zps2b8994a8.jpg

Any help is very much appreciated!