In the common downloader, after you browse for the folder containing the ROM, did you click advanced and check the following files are ticked:
Sorry if this isn't any help to you, where's Miro when we need him
Otherwise, I don't understand why it wouldnt work because our phones are the same, presumably you bought it in England like I did so the hardware should be the same. Mine worked like a charm. I can flash back and forth with no problems.
Also, are you using mi7ROM_3_8107.79.zip ?
Also, check your SD card isn't locked up before the flashing process. I think a freshly formatted SD card works best. Good luck!
I'v now tried to flash on 5 different computers. All i get is "Running Ram" and 0% progress, till the battery in the phone goes flat
Don't know what SD card you're using, but the toshiba SD card that came with the phone caused me no end of problems such as crashing so I had to replace it with a... sandisk I think it is.