You can remove it after one month or anytime thereafter without it affecting your contract. I don't think you'll get it cheaper £13.50.
Red button is coming soon. 2011 probably unless Uncle Rupert can delay it further.
In case you're not aware, you no longer get Sky Sports 3 free with SS1 so if there's a clash and your favourite sport gets shunted onto SS3 you won't see it live. I suspect this may be a tactic Sky will use more frequently since VM don't have SS3 & 4 in HD.