Guys you should def join Unison, I am a steward for them and they are really good and have helped me with difficult managers in the NHS. The RCN are good for courses and Queens like you to be with them, it's like a prestige thing, but it won't go against you if you are with Unison. If you have real issues and need representation then Unison are the best trade union, the RCN are a professional organsiation and not affiliated with the TUC (Trade Union Congress).
Sorry to go on but it's just a bit of advice!
Sooooo excited about Monday, I can't wait!