I have the N73 on 02, purchased from the carphone warehouse. Firmware is the July 06 one. No branding at all. Do I upgrade now or wait for something from O2 or the appearance of the n73 on the software update nokia uk site? Confused.

The N73 is now included in the software updater, I updated mine yesterday, no problems at all!
Just follow the descriptions and instructions regarding N73 in the Nokia FAQ.