Posted: Yesterday at 13:05
They look like sawfly caterpillars, perhaps the last of the summer broods which normally overwinter as pupae. However, even they don't do much damage other than defoliating roses, gooseberries etc. There are about 400 species! Could be beetle grubs, of some species or another, probably harmless to live plants and very likely feeding on rotting wood somewhere. They'll have finished growth now and are waiting to pupate before emerging, as something wonderful, in spring. Either way, they're not wireworm, cockchafer or vine weevil so be pleased!