I notice we have carrot problems which is a shame as we have just started pulling them although I think the actual carrot under the soil is fine. Looking in my book “The Vegetable & Herb Expert” by Dr. D G Hessayon (a great series of books these “Expert” series) it looks to be Carrot-Willow Aphid, greenfly. For some reason our garden is covered in blackfly and it looks like greenfly too. I don’t believe I have seen so many before, I wonder if this is to do with the constant hot and sometimes very humid weather. The distorted leaves suggest aphids which it goes on to warn about the more serious transmission of motley dwarf virus which discolours the leaves. It goes on to say growth will be distorted if the attack is in the seedling stage, good fortune for us then that it has just taken hold now.
I suppose it is all a bit late now to do anything, but the whole blackfly, aphid thing is starting to get on my nerves and so plan to spray everything with water and washing up liquid daily in order to stop these things building up.