Hey Helen,
I'm in Melbourne right now, and will be here until April/May, so if you need a hand with anything let me know! I haven't stayed at the Base in St Kilda, but I stayed at base in Brisbane and it was nice enough.
You could apply for that, but if they want you for more than 6 months they'd have to sponsor you (I'm 99% sure I'm right there..) as you a working holiday visa you can only work the same job for 6 months. If I'm wrong I'm sure somebody will correct me!