FWIW, as the season is half over mlb.tv is quite cheap now. You can get a normal sub for $39.99 (about £25) or a premium sub (which lets you also watch on iOS or Android devices) for $49.99 (about £32).
---------- Post added at 10:51 ---------- Previous post was at 10:47 ----------
Annoyingly, US-based TiVo customers have access to an mlb.tv app. Wonder how likely we are to see that one over here.
http://mlb.mlb.com/mlb/subscriptions...p?product=tivo