Coders have been coming up with all these homebrew "changer" apps lately which allow you to, well, change various things in your PSP. We have gracz54's PSP Mac Address Changer, and there's also Aserto's PSX GameID Changer.

And now, to add to that ever-changing list of changer apps, here's another one from Dabomstew which will allow you to change the version displayed in 3.03 OE-A system settings without hexediting or manual flashing.

Usage Instructions:

• Check that your psp is on firmware version 3.03 OE-A by Dark_AleX. If it isn't, you cannot use this app.
• Connect your psp to your pc via usb. Then copy the vc folder supplied to X:PSPGAME150 (where X is the drive letter of your psp).
• Disconnect USB and run the version changer like you would any homebrew app, and follow the onscreen instructions.
  

I was able to update 3.02 OE-B to 3.03 OE-A with a custom version on 3.02 OE-B, but im not sure about the updaters to go to a new release on the same kernel eg 3.02 OE-A to 3.02 OE-B. I guess we'll see =P If it doesn't work, you can easily change your version back to default.