With the 'Game File Transfer over Local Network' feature in Steam, you don't need a fast internet connection; 'just' another system on the LAN that can serve the files.

Fairly common for those with full-powered gaming desktops and Steam Decks, and soon, Steam Machines.

Telemach, 2Gbps symmetrical - 34,90 EUR, Croatia. Flat rate, also includes flat rate landline to in-country mobile and other phones, but haven't bothered to even install that.

The UK isn't exactly cheap, but the >1gbit packages tend to be in the 70 USD per month range, maybe uptowards $100 a month by the time you get to 5Gbit on the more traditional providers (sky for example)