In case this is copied, go to the original site which should be http://philatwarrimoo.blogspot.com/2011/02/howto-vodafone-uk-nexus-one-to.html
A friend made this great guide.
I have to same phone with the same Vodafone UK ROM and I kept my log of what I did in case it might help others.
All of the screenshots are from the above blog.
All the following stages are similar. The first is a little different, but the others are virtually the same - the differences being the URL to get the file, and the name of the file to copy to your phone's SD card.
Sometimes the phone will automatically reboot after the installation of the update.zip file - other times you will need to manually reboot it by selecting the right menu item. All of this should be obvious.
Just follow these steps in order. If you get lost or miss a step, just start again (I did that a few times).
I do not know the original MD5 sums of the files listed below, but so you can verify that you get the same file as I did, here are my MD5 sums:
passimg.zip (the file extracted from the file above)
Android Version: 2.2 Baseband Version: 32.41.00.32U_5.08.00.04 Kernel Version: 184.108.40.206-27237-gbe746fb android-build@apa26 #1 Build Number: FRG33
Android Version: 2.2.1Baseband Version: 32.36.00.28U_4.06.00.12_7 Kernel Version: 220.127.116.11-27240-gbca5320 android-build@apa26 #1 Build Number: FRG83
Android Version: 2.2.1Baseband Version: 32.36.00.28U_4.06.00.12_7 Kernel Version: 18.104.22.168-27240-gbca5320 android-build@apa26 #1 Build Number: FRG83D
Android Version: 2.2.2 Baseband Version: 32.36.00.28U_4.06.00.12_7 Kernel Version: 22.214.171.124-27240-gbca5320 android-build@apa26 #1 Build Number: FRG83G
Android Version: 2.3.3 Baseband Version: 32.41.00.32U_5.08.00.04 Kernel Version: 126.96.36.199-59423-g08607d74 android-build@apa28 #1 Build Number: GRI40