Here: https://mega.nz/#!3dgBmKzQ!Ve7-ZD7O6BBZvUkQVyJdkpmftjPcpzVTm-YzNRjJ8ss G510 firmwareG510-0100CAndroid 4.1Emtion UI V100R001C479B193 United Kingdom Channel Install with custom recovery Thanks to worstenbrood for his very handy tool: http://forum.xda-developers.com/showthread.php?t=2433454
Install custom recovery again then flash this: https://mega.nz/#!HB4GVa5B!Bbh-k3i-PlNpLOZuPga-WUTNXskSTvBSSXaWgC9YoDI It is b170 stock. Then from the stock ROM I believe you have an option to update from local source(dload folder in root of SD card)
Look somewhere like here: http://consumer.huawei.com/en/mobile-phones/support/downloads/g510-en.htm Use a PC to put dload on SD card. There are detailed instructions as part of the download. Can you remember the version of firmware on your phone? You can only flash the same outer higher.