If it is the dreaded Vine Weevil grub they are usualy creamy white with in a 'c' shape , half inch long plumpish / well filled out. They are orange/brown at one end.
They only attack the roots , as far as I know .Sometimes the first sign is yellowing leaves.
This is what I do for shrubs and plants- I dig them up and wash the roots in soapy water. I then replant in a pot . I then give them a good watering of the Vine Weevil solution . but I dont know if it is safe to use on veg. A garden center will advise. Buying the nematodes could be expensive specialy if they are not the vine weevil. Can you put a picture on here or failing that take some into a garden center. It is true the menure needs to be old and well rotted / have no smell .
I have a suggestion to make, some people grow in pots to eradicate the problem - but youd still need to keep check , a friend of mine grows in old tyres his carrots , he stacks 3 together , uses new bags of compost . growing carrots this way keeps away the carrot fly. your radish could be grown in a pot, and if your butternut squash is a bush type you would be alright in a largish pot. until you get your garden sorted out for next year growing veg in pots is an alternative - admitted not quite the same but at kleast you have a taste of your freshly growm veg!
If it turns out to be a fly infestation from the menuer then this can be treated with sprays again ask at a garden center. At least you have time to work on your soil to get it right for next year .
Let us know how you get on . take care.