u/Ok_Maintenance305

Hi there, I live in South Wales and recently moved into a house that has a beautiful grapevine. I’ve not had a garden before let alone a grapevine, but I have been trying my best to look after it. I read online to water once a week, I have been doing more like twice with the heat. However, lots of the leaves have now fallen off and dying and the grapevine looks very heavy. Any help on what to do with it? Do I need to trim it? Is it a lack of water that is causing this and what do I do? For reference the whole Grapevine is watered in one area at the trunk and I can’t access the other roots. Photos attached. Thanks in advance!