A good old-fashioned pruning hook on a pole is good for a) keeping things under control and b) harvesting fruit you can't reach. Have a sniff around your local auction house when they've a general sale on, as you may well find gardening tools there.
Grapes do grow well enough here in the UK. I have a white variety called Phoenix, which crops pretty reliably, albeit it's not a dessert variety. But it makes fabulous grape jelly, which is just *the* thing to have with peanut butter on toast. Grape vines do need regular haircuts if they're to be kept under control, but if you're looking to screen a fence or wall, then yes, they'll do nicely. Do run a length of heavy gauge wire along where you want to train it, so that the tendrils can curl around it. And I'm somewhat further north than you, and if I can get a good crop of grapes (mine are trained around a southwest-facing porch), you shouldn't have an issue
Hazel is great for coppicing, and if you've a lot of straight thumb-thickness growth, you won't ever need to buy garden canes.
Your plums could be anything from cherry plums (small, either round or oval, yellow or red, and earliest variety to ripen), greengages (larger round fruits) to dual-purpose like Victoria, or purely culinary such as a damson. You won't know for sure just yet, as most plums largely won't be ripe till early / mid August, or a bit later than that if they're damsons. if you've good quality dessert fruit, just eat them! They'll be so much nicer than anything you can buy in the shops. If they're damsons, then anyone who makes jam or wine would be grateful for them.
If the mystery berries are round and grow in clusters, they could be rowan - edible, but not raw. They must be cooked or frozen first, albeit the taste is bitter so you can't just eat them. In Poland they put the berries in vodka to make a liqueur called Jarzębiak, and in Scandinavia, they make rowan and apple jelly that's spiced with cinnamon & clove. It's bloody lovely, btw, good on toast and with cold cuts.
Should you have a wealth of fruit that's only suitable for preserves (damsons, rowan, cooking apples), it could also be worth seeing if the local WI branch can use it. It's a shame to let anything go to waste.