I understand you 100%. My telstra rom went out the window quickly. I never saw so much branding and the US carriers are good for that. lol. No reason to do a pim backup as the 1.49 signed telstra rom is available for download and can be put pack on if needed. I have it and will find you the link if you want to download it.
First thing you will need is HSPL. That will allow you to flash any rom on your phone that you want. Be warned to only flash using your pc and activesync. You dont want to install any rom using the storage card, as that will possibly change your spl and you wont be able to flash back if needed. Good info and HSPL here.
http://forum.xda-developers.com/showthread.php?t=611433After you have flashed the HSPL then you can flash your rom. Have you picked one out yet? I strongly suggest if looking for wwe (english) you choose 1.66 from HTC.com from europe or southeast asia. Links to both on this forum. I chose sea because it didnt come with co-pilot. Trying to save space. But I have settings on keyboard to use chinese characters. Europe version wont have that I believe. Cooked roms can be newer,fancy and quicker but most have bugs and instability. Especially if you are new this may not be something you wish for.
Once you have your hspl and rom it takes about 10 minutes. Actually alot easier than you think.