Grab GENERIC_MAIN, choose what FS you want depending upon the languages you want it to contain, and download a suitable custpack with it. You can find what langauges each FS contains here. A guide on how to flash it all to your phone. Since you are using a w810i cid 49, I would strongly suggest that what you download be R4EA031 cid 49, it is easily the firmware with the most amount of patches out of all the w810 firmware. It is also cid 49 which makes it just that much easier to break into with far than if you upgraded it to cid 50