[myTouch 3G, Magic General] crypticc:
You could do what I did which I've summarised below. There's probably more backup steps than is necessary, but you can never be too careful.

There's loads of guides out there with the guides and detail, e.g. http://xdaforums.com/showthread.php?t=519523

but they seem to branch in and out of methods quite a bit. I've added a few links to the pages I used for the detail.

The method I used is the 1 click backdoor, which also disables OTA updates to stop it being closed in the future I think.

First off, I'm a Linux noob and managed okay because the apps are so well thought out, but this is all done at your own risk.

Secondly, your uk Magic Vodafone prob has 32b board, not 32a.

(There's plenty on this forum. Or the Cyanogen one on the Dream forum works for 32b too.)

You can check with extra step by powering off, then on power again while holding back button. Last digits at top tell you the board details. Menu button gets you back.

0) Install the Android USB driver, connect, mount, then disconnect, etc.

http://dl.google.com/android/android_usb_windows.zip

1) Use google to sync all your contacts, etc. to google account so restore is automatic.

2) Use Astro to Backup your apps etc to the sd card

3) Goto wireless settings, mobile networks, apn, select and make note of your vodafone UK APN details (so you can type your 3g settings back)

4) Use USB to copy your SD card to your PC

5) From your phone, Download Cyanogen recovery. Don't run yet.

http://www.ryebrye.com/blog/2009/08/16/android-rooting-in-1-click-in-progress/

( This basically automates the rooting and booting to this recovery image : http://xdaforums.com/showthread.php?t=523558 )

6) From your phone, Download a rom image; the 32b board you prob have in your UK Magic allows you to use 32b ones, I used the Cyanogen one here.

http://xdaforums.com/showthread.php?t=537204

7) Use Astro to move the rom file from \sdcard\download to root of \sdcard

8) Run Cyanogen recovery 1.4 1-click root installed in 5.

Use Backup recovery image

Use Flash recovery

9) Poweroff, home + power to get into the custom recovery image

10) Select Nandroid backup to create new backup (this copies your phone to your SD card)

11) Reboot. Repeat 3 to get the backup of the nandroid folder, and the recovery image created in 7 and 9 onto your PC

12) Run Cyanogen recovery 1.4 1-click root installed in 5 again.

Flash recovery (this makes next boot 'special')

13) Reboot. Poweroff, hold home + power on again.

14) Select WIPE (You did backup your apps and SD card data right?).

15) Then select apply any zip from sd.

Follow instructions to install the Cyanogen rom image you moved to the root of your SD Card in 6 and 7

16) Wait 10 mins or so. The last message about writing root or whatever doesn't explicitly say finished.

17) Reboot.

If you have reboot hang, most people report is because missed WIPE step. Otherwise consult the relevant forum for the Rom you downloaded.

18) Do the new user settings thing. The activation and sync will fail cos you've not got 3G yet.

19) Goto network settings, advanced, APN, type in your vodafone UK APN details (so you can type your 3g settings back)

20) Done

21) If you've got Cyanogen Install the updater from marketplace (search for Cyanogen), or here...

http://xdaforums.com/showthread.php?t=544663

I also installed:

Audio resources unzipped to your SD Card root from the Cyanogen rom pages, this reinstates notifications and ringtones I guess were removed to allow the memory obsessives to keep their phones clean.

SetCPU from this site, to override the default Cyanogen high overclock settings when phone is sleeping.

Cheers

Chris