with sky you will have to pay BT ontop.
some deals, will pay the BT line rental for you
SOME companies, are priced in such a way, that having thier broadband, phone, and cable TV package is CHEAPER than paying BT for line rental alone, let alone before you make any calls, as they include it all.
A mobile bb dongle or card, is like plugging a mobile phone into the computer.
if your not using oodles of bandwidth per month (just browsing and emailing etc), and have ok reception probably perfect!
and you can use that anywhere you like, on the same account
free wifi in places like wetherspoons is the same as connecting to a wireless network at home, only you can go an ask them for thier passwords at the bar!
be aware, using free wifi, that it is possible for people to sit nearby, with “fake” log in pages being transmited from thier laptop, so when you go to log in, and it asks for bank details, your really typing them onto thier own laptop.
check with the staff in-house how the connection setup should work, and make sure it DOES work as they say it should.