I have purchased an O2 8300 and want to use this on Orange.

How do I get rid of the O2 stuff and install the Orange info. This would include the start-up page, wap and internet connections etc.

It may sound daft but I am struggling and RIM won't help, nor will O2 or Orange.

PLEASE!!!!

The o2 branding when you turn on the device can not be changed.

Do you have an BlackBerry Data Plan on your account?

Yep I have one with O2 on a 8300 and one with Orange on 8700F.

I want to use Orange on my 8300!!

If the device is unlocked you can use it with any sim card. As NJB said above, you can't change the branding of the startup page. However, when you insert the sim card it will pull whatever services are available from the new sim card. There's no need to rebrand or reload an OS just for changing carriers.

So, when I unlock it it will just take the info from my orange sim and upload the correct info?

If this is the case, why is there a specific download depending on the carrier on RIM's www.

That's correct. Each carrier releases a device with a software version that they know how to support and write literature for. All the OS's are written by RIM and are interchangeable (within each device model line.)

Yes, unlock the device and insert new sim. All will be well.