Okay, I probably know the answer to this already but I just want to set my mind at ease over the issue.
I was asked to flash a "Halo 3" edition 360, Philps/Benq drive. Pretty straight forward, had it done in 30 mins with iprep. I wasn't able to test the box as the guy didn't bring the power brick with him and I have 2 Falcon boxes so the bricks are the wrong type for the Halo box. Anyway, I told him to check the box when he got home, and loaned him my backup of FIFA 09 to try it with. He rang me about an hour later to say that when he ran FIFA it came up as being the wrong region. On questioning him further he admitted he had bought the box second hand and had only played a handful of games on it, Gears Of War, Halo 3 and Hour Of Victory.
Now I'm pretty sure that EA region lock their games and at least Halo 3 was region free, so I'm thinking whoever owned the box originally has imported it, realised it won't play European games and has traded it in and this guy has bought it, realised it won't play European games and reckoned getting it flashed would change the region.
I've explained to him that, even though it is set as a UK machine in the OS, the region is hard coded into the system.
So, am I right in thinking that there is no way the region of a 360 can be changed by flashing the drive?