I received my Unlock code, and am just writing to say it works perfectly.
I removed my T-Mobile PAYG SIM card, replaced it with my partners Orange PAYG SIM card, and turned on the phone. I was prompted for my Phone's PIN code when booted, and then prompted for the "Network Unlock Code". I entered the code I received by email, and then got a "Network Unlock Successful".
The phone then connected to Orange and notified me of a couple of my partners voicemail messages. I then switched off and reinserted my T-Mobile PAYG SIM card. Upon rebooting, I was prompted to relogin to my Google account (for sync'ing purposes). I reconfirmed my password, and seems to working normally again.
Many thanks for the Unlock Code providers. An excellent service for a very reasonable price (£12). I can now travel abroad and purchase a cheap local SIM card to save in roaming internet costs.
Louis