[starry]

Of my beetroot leaves turning yellow just found little grubs on the INSIDE of the leaves and tiny eggs which I picked off on the underside of the leaved yuck horrid things, already found loads of vine weevel larve in my begonias yesterday 

[Salmo]

The grubs in your beetroot are beet leaf miner. Usually just leave them alone but squidge if you want to. They will soon stop feeding and drop into the soil to pupate. There will be another generation in late August which then pupates to overwinter in the soil. When the flies emerge in the Spring they look for the nearest beet. Hence rotate your beet.

More of a problem in perpetual spinach and chard where their tunnels in the leave can spoil the crop.

[starry]

Found them in the little gem lettuce too, I have never grown either in the position they are in now, but have squished all that I can see and removed the eggs just hope they havent been affected to much as they have slowed down