Boy, grape vines and anything else in the grape family is beloved by many different species of moths. I get eumorpha achemon sphinx and eight-spotted forester moths on my Virginia Creeper, both of which I love and have raised. But, in the UK, I don't know what you would have. Do you see rolled leaves on it? Some kind of spring moth would do that, as well as the grape leaf roller. Check these out by googling "Grape Vine+moths+United Kingdom" and see what you might come up with. Many moths are generalist feeders, meaning they will eat just about anything. There are few, however, that are specific to grape vines.

Susan

I've found two different beetles really chew huge holes in bigger leaves and eat the youngest ones entirely, and Japanese beetles seem to love mine, though they only recently arrived in my garden and most likely will prove a major problem. Theres' also a much larger beetle with beige overall shells with black spots, which I've never identified, and that one loves them as well. As for not seeing anything, I'd assumer you have looked very carefully, and in some cases those beetles are very good at conceiling themselves and you have to look hard to find them. Nocturnal munchers that live elsewhere during the daylight hours are also good candidates, though most caterpillars will stay with the food source as will the beetles. I'd guess snails love them as well, and those would depart during daytime hours.

I think what you are talking about are the Harrisina Americana caterpillars. I moved to Central Florida this spring and noticed a wild grape vine on the ground. I trellised it and hoped for muscadine grapes. The plant was really lush at the top of summer and til last week was nothing but a vine thanks to these yellow caterpillars with black stripes and tufts of white hair. They lined up side by side and reduced the leaves to nothing but their veins. I'm disappointed that they ate so much of the vine but I don't approve of insecticides being that I'm on well water. I am enjoying some regrowth now that the caterpillars have went to cocoon. Wish me luck on the grapes ;)

Here is a link that might be useful: Dave's Garden