I do blame Nokia for this confusing situation, not least the strange concept of backing up a brand new phone before updating but there is more to it. It's true that there isn't much you can do except send the phone back via your service provider and have it re-flashed to the original firmware. I've given the solution for those who have yet to upgrade elsewhere and here it is again....
Sadly, when you launch the Nokia Software Updater, it unfortunately reminds you to use the 'Nokia PC Suite' to backup your phone before continuing but don't do it! If you want your activation key to be saved, you *must* use the latest equivalent NSeries PC Suite utility which is confusingly named 'Content Copier'.
I backed up my brand new O2 branded 8GB model (v11.0.026), updated the firmware to v15.0.015 and then restored the backup and Spiderman runs perfectly.
I guess the Software Updater is the same application which ever PC Suite edition you use. Nokia need to tweak it to detect which phone you're using and what versions of the PC Suite you have installed *beforehand* and then advise the appropriate method to backup the phone. Ideally of course, the activation key should be included with the firmware update but these are special edition models so I’m guessing Nokia doesn’t want everybody having the key.
You could try a phone reset to put the phone back to original settings but I don't know if this overwrites the newer firmware. *#7370#