It's now on the forthcoming list for the advisors at customer services... you'll be looking at a month I'd estimate... possibly less. The D900 appeared on my list of current handsets yesterday, so the ultra slim samsungs are just about ready to all be out.
No idea... bear in mind that suppliers such as dial-a-phone and P4U often work from a central stock that isn't locked to any specific network. If the manufacturer has released the phone they'll have it. Buying direct from O2 just means you get some POS O2 branding on the software, but external suppliers such as P4U don't generally perform upgrades... they open a new contract and take the comission and get you to concel your old one.