Gooseberry sawfly larva. They will strip the leaves almost overnight. No real cure. However the bushes rarely suffer too much from the loss of leaves. Give them a high nitrogen feed now to encourage new leaf growth. Next year keep an eye open for the first signs of leaf eating and spray with whatever you choose.

yes this is typical of sawfly larva. Do as Owdboggy says re feed etc.
other than chemical sprays you could use a pheromone lure [if available to you]
hang the lure close to the bushes at the end of May and the males will fly into the trap. The females wont then be mated so no eggs.

Thank you so much will do

Hi Poundy, hope you are still looking at replies! This pest overwinters in the soil under the bush. So I tried spreading some black plastic (pond liner trimmings so nice and heavy) underneath in the autumn,hoping that the little blighters wouldn't be able to get out. It works. If you can nip the problem before it starts you can avoid chemicals and traps altogether.Your bush should recover next Spring, they usually do even if almost completely stripped. I feed sulphate of potash in February when they get pruned.