You can get NHL.tv for $24.99 a month. I'd recommend getting a VPN alongside it, as games that are televised in the UK (on Premier Sports) are blacked out for 48 hours. A VPN will mean you can watch every game.
Or you can get Premier Sports which is £9.99 a month, which I believe you can subscribe to just online if you don't already have Sky or Virgin. They don't show every game, but they show a lot, and then all of the playoffs. I'm not sure if you can watch games on-demand like you can with NHL.tv though.
The regular season is a bit of a slog, I tend to watch highlights on
www.dtmts.com for a lot of the regular season. Then I pick up NHL.tv towards the end of the season and for the playoffs. The price comes down quite dramatically by that point.