Re the citizenship, your bub will automatically have dual citizenship. When you want to travel you just have to fill out a UK passport form and get the Dad to sign it...but you'll prob need copies of his BC etc. When I did my kids passports (i'm a UK citizen their Dad is Kiwi citizen, Aus perm res) it was actually easier to get thier UK passports than their Aussie ones and they were all born here.

HTH