welcome to GoY.
this sounds like sawfly.
this what the RHS says.

•Severe defoliation of the bushes can be caused by the caterpillar-like larvae of one of three species of sawfly
•Larvae of the common gooseberry sawfly are up to 20mm (almost ¾in) long, pale green, with many black spots, and black heads The adults are winged insects; females are 5-7mm (up to ¼in) long and are yellow with black heads and black markings on the thorax; males are similar but more extensively marked with black, including the upper surface of the abdomen
•Larvae of the pale spotted gooseberry sawfly are slightly smaller than those of the common gooseberry sawfly and have pale green heads. It has one generation a year with larvae present in May and June
•The small gooseberry sawfly can have up to four generations of pale green larvae from late April onwards
•The larvae of some moths may also eat the foliage of gooseberries and currants

Control

Non-chemical control
•Regularly check the plants from mid-April onwards for sawfly larvae and pick them off by hand
•A biological control (pathogenic nematode), sold as Fruit and Vegetable Protection, can be watered onto infested plants. The nematodes enter the bodies of the sawfly larvae and infect them with a bacterial disease. This nematode is available from some garden centres or via mail order. The nematode should be applied during cool damp weather

Chemical control
•Spray when young larvae are seen, with an insecticide approved for use on the appropriate food plant. Make sure that the manufacturer's instructions regarding maximum number of applications and harvest interval are followed
•Suitable insecticides include the contact pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), deltamethrin (e.g. Bayer Provado Ultimate Fruit & Vegetable Bug Killer) or an organic pesticide such as pyrethrum (e.g. Defenders Bug Killer)
•Plants in flower should not be sprayed due to the danger to pollinating insects

It is very early for sawfly - its been a funny season. Normally the bush will recover but it will take a while.

The wild Gooseberries in our hedge row get stripped every year and still produce good fruit. All I ever did when I grew them, was to give them a high nitrogen feed to help the bushes grow new leaves.