Grape vines for the south west

I planted a cheap Merlot vine I got in one of the German supermarkets and here is a video clip of it with some grapes five years back. It is planted near the edge of the tunnel in north county Cork which I do not try to keep insulated as I read it is important for the roots to get some amount of cold in the winter for them to fruit well. The vine is productive but the skin might be a bit thick for an eating grape although that is all I do with part of the crop which mostly gets left for the birds in recent years. I think most vines should grow OK in the situation you describe but a soft skinned one might be better for eating. Monty Donn from BBC Gardeners World recommends thinning out the grapes to help the fruit get bigger and tastier but I have never had the patience to do this and do find some of the bigger bunches can have a few moldy fruit near the middle of the bunch. Just don't have the right set up in the kitchen to brew some wine but have to give it a go some year as it is a shame to not be using all of the fruit. I visited Glebe Gardens near Baltimore in west Cork before and I think they mentioned having a nice eating grape in a polytunnel but also think they might have mentioned having a problem with wasps being attracted which might be more of a problem with soft skinned varieties of grape. If you get in touch with them they might be able to give you some more information on their experience as it was a few years back that I visited there.