Small white/silver worms in potting compost - fungus gnat? Help plse
 

I have a pestilence of small (up to 6mm long) silvery white worms and tiny
brown flying thingies in a bag of potting compost. Any idea what these
might be please? I suspect they might be fungus gnats according to what
I've read.

More importantly, any suggestions on how to be rid of the wretched things.
Problem is that I potted up a few seedlings a while back and the compost is
wriggling with the little blighters.

Many thanks

Sunbeam.