Thank you for this awesome guide. My phone originally had the Voda B960 firmware and I installed a custom ROM with the hacked bootloader. When following this guide I had trouble with the B952 update.app, I think this is because the partitions are different or something (I'm new to this Android dev stuff).
But anyway, instead of force installing update.app I installed these 2 using ClockworkMod Recovery:
Then carried on the tutorial as normal, and it seemed to do the job!
Another thing, when I restored my phone (which had a custom ROM installed), I couldn't boot. I also got round this by installing the custom ROM again as usual, and then restoring everything else except boot from my backup.
No guarantees if this will work for you, but it worked for me :).
Let me know if you found this useful or if I'm doing anything really stupid here, thanks.