What you really need to understand is that as long as you have an ethernet (network) port on the computer you are trying to connect to the internet, then the standards of TCP/IP take over and you need no specific OS-based software to install to get it all working.
I use BT, and have done for years both as a network administrator and personally, and although sometimes it has not been the cheapest connection available, you get a reliability which (in my experience) has not been matched by anyone apart from Pipex, who do not offer the full package you are looking for.
Once you have chosen a supplier, do not use the 'free' USB-connected 'modem', but instead spend £30-£40 on a (wireless if required) ethernet-based broadband router, which will allow ANY connected computers to access the internet, not just the one with the USB-connected modem attached!
You will find this a much better solution, and it should be completely hassle-free!
Good luck.
Nig.