a bit of insight from across the pond and my first post too! i read this forum with envy to be honest, I’m an all grain beer brewer (which we're really good at in the UK) who has been making wine from kits in addition to beer for a few years.
I read about you guys fermenting 100 litres in bins and ageing in 6 gallon carboys, or even on oak for years, and tbh I can only dream! You can buy fresh grapes at harvest and buckets of frozen juice, some of you even have your own vineyards!
It's like a wilderness in the uk by comparison! We can get all the winexpert ranges here and they’re regarded as the best. There’s literally 1 (one!) brave and intrepid importer in the uk of some of the mosti mondiale range and he sells very competitively but most winemakers here have never even heard of his store or MM. We also have the ‘on the house’ range which is a local branding of one of the big North American producers by all accounts but idr which.
Other than those, who produce mainly 23 litre kits, we have some cheap ranges that are utter garbage tbh but keep the budget conscious entertained somehow. One example is a kit that makes 23l out of 3 litres of concentrate with kilos of sugar added and sell for less than the equivalent of 20$
We can get a limited range of winexpert 1 gallon kits (4.5l,) but making just 6 bottles is a pain in the arse so I’ve only ever done two which were whites, PG and chardonnay. They taste ok to be fair, but for not much more money per bottle I can buy much better in the supermarket (grocery store!)
so in the uk I doubt there’s anyone at all that makes more than 23 litres (5 uk gallons) at a time. There might some who start a number of kits at once, but it’ll be in individual 30 litre buckets, not 100l rubber dong growlers or whatever you call them