You are correct that the ML install will create a ML Recovery HD, and if you boot from that Recovery HD on your drive it will prompt for an AppleID and reinstall ML.
But you need to get past that and go back to the Lion install that came with your machine. To do that you want to get to Internet Recovery by booting with command-option-r. That should boot from the firmware based Internet Recovery and not the Recovery HD (which will go to ML). Once in Internet Recovery, start Disk Util and format the whole drive not just the Macintosh HD partition. To do that you will want to click on the drive name like "128GB Samsung" or whatever. After a full drive format proceed with the install. Yu not be prompted for an AppleID as you are now installing Lion linked to your serial number.
If you have trouble getting to Internet Recovery you can do the same thing by booting from a recovery USB and doing the full disk format then rebooting with command-r.