There's no new information in this post that doesn't exist elsewhere - I'm just putting it here as a reference for myself so that I've got everything in one easy to find place.
- Install the driver from Dell for the Streak. Package R291096.exe found at http://www.dell.com/support/drivers/uk/en/ukdhs1
- Create a folder on the root of C: called Flash 350
- Go to http://forum.pocketables.net/showthread.php?t=9694 and download the files from the here link in Step 6. Extract these to the Flash350 folder
- Go to http://forum.xda-developers.com/wiki/index.php?title=Dell_Streak#Official and download the 350 package (click on 350 on the left of the table) and the Recovery package.
- Save both of these to the Flash350 folder and rename the pkg file to update.pkg
- Plug in the Streak via USB and copy only the update.pkg file to the root of the SD card
- Unplug the streak and power it off. Take the battery out for good measure and then put it back in.
- Boot into fastboot mode - hold down the camera button and then press power. You should get a white screen with Fastboot in the top right corner. click on Fastboot.
- There'll be a message of "Wait for USB Fastboot detect" in the bottom left corner. Plug the streak back in via USB. The screen should change to Fastboot_Mode.
- back in your Flash350 folder double-click ApplyRecovery.bat. when it gets to the pause stage the Streak should display a completed message. Be ready to hold down the volume buttons...
- Once you're sure it's completed, press enter on the PC keyboard to reboot the Streak. as soon as the Streak goes black, hold down the volume up and down buttons until recovery mode starts.
- select option 2 "Software upgrade via Update.pkg on SD card" with the camera button. Press camera again to install which takes about 10 minutes.
- When it boots it'll be in Korean - press the button in the bottom right (which is Change language) to choose English.
- Go via Software Update to download the 2.3.3 update which is the last official Dell update.
Credit to the following websites for where I got this info: