Sounds as though it could be gooseberry sawfly larvae. Give them a spray with Bayer Provado Ultimate Fruit & Vegetable Bug Killer or similar and that should sort them out.

Once you've had this it tends to recur so be on regular lookout for it early on next year - a light attack can be warded off by simply removing the leaves with the newly hatched caterpillars on it, before they have grown and dispersed, as you won't want to be spraying while the fruit is on the bush if it can be avoided.