Well, so for electrical work I know that Northern Grid will do any reasonable upgrades for your network for free, just because that's part of what they exist to do. I asked for an upgrade to 100amp connection to my house, they did a survey and answered that they would need to dig out the whole cable from my house to the street and replace it with a new one. "Of course" - they said - "we would put everything back at is was once we're done". Cost? Absolutely free. Well, funded by the taxpayer I guess. I don't see why openreach shouldn't be the same - if your house isn't on the fibre network, they should connect you as that's literally their mission statement. I guess for really complicated cases the cost could be shared or something, but quoting people 50k for connecting a domestic property to fibre shouldn't be acceptable.
But it's not just 50k for a domestic property, it's 50k to dig up a road, and tunnel under a stream.
I wasn't aware that electrical connections were done for free - Citizensadvice [0] calls out that for gas if the connection is far enough away you'll have to pay for it. I've heard anecdotal costs of <£1000 for a straightforward connection that doesn't involve digging up a road.
Get a quote for a mains gas connection or an electrical connection and you'll find it in the same ballpark.