[Upgrading, Modifying and Unlocking] JethroUK:
Post Updated 19/7/13 right here to save you reading the whole thread:

Bought Huawei G520 (quad core) direct from China £125

It starts up in Chinese, but with a little help from Google I managed to change it to English quite easily

Just look for the "A" icon and then it's the top option to change to English

(If you put an English sim in it first, it defaults to English anyway)

No Google apps!

I didn't anticipate the China vs Google being a problem, especially since "Android" is "Google"s own OS. How can you have an Google OS with no Google apps, but you can, and China have.

Anyway I spent the next 2 days solid trying different solutions, different rooting tools, flashing tools, downloading Google apps by apk (some do work but most just close down & cant login)

Locked up the phone in my desperate attempts to install virtually anything....but...

....I managed to find the Huawei G520 000 Official Stock Rom here....

..UPDATE 19/7/13) have since found newer official B192 version here - havent tried it though....

...either of which is easy to install.....unzip the folder and copy just the folder called "dload" to the root of your sd card - remove your G520 battery for about 30 seconds...refit the battery....hold both volume keys with one hand...now hold the power button too until the process starts (about 15 seconds)

Even managed to install Clockworkmod (whatever that is), dont ask me how,where, just a result of trying so much software I guess - When I saw it I figured it was rooted, but still couldn't install anything with it so I guess it was still not rooted

Anyway I discovered that the "Bootloader" is locked on this model - was directed to.....

Huawei website where you can request bootloader code (16 digit number)

....and found out the same as you, that the G520 is not listed - Dang!

Decided to ......

send an email to Huawei just on the hope they might respond

.... - I wrote down all the details as required from the official form and sent it.....Would you believe it, they only went and sent me the bootloader unlock code THE VERY NEXT DAY - in fact it was within about 8 hours - BRILLIANT!

...you need a usb driver to perform the unlock procedure and to be honest i installed loads so i cant remember which one to credit but i found this

.........official Huawei Generic USB driver...

...it should work although is does make you wonder why they dont link to it in the first place? If I remember right, if its the correct driver and you connect you mobile in USB Debugging mode (Settings > Developer settings > USB Debuggin = checked) the PC says "connected in ADB mode"....

Followed the official Huawei bootloader unlocking procedure...

...and Bobs your uncle "Your bootloader is UNLOCKED" - Yaaaaaaaaaaaayyyyyyyyyy

I thought the rest was easy now - nope

Tried a million and one rooting/flashing tools, still wouldn't root (I downloaded "Root Explorer apk" to my mobile to try and access the root directory and thats how i knew it wasn't rooting - nearly gave up on the whole idea - figured it was root locked for ever

The G520-000 is Exclusively Chinese so I started searching China, which was difficult, not just because it's Chinese but you cant use Google because for the same reasons it doesn't search China - so I ended up using the G520 browser its-self to search (got millions of hits because its very popular in China) and if it looked interesting I emailed link back to my PC where Google translated the web page - loads of forums about flashing the G520-000

Anyway I found a buzz on Chinese forums .......

about this tool

....and can you believe it - It rooted it in 1 minute

It's in Chinese and installs Chinese superuser...but its easy to follow - Moderators that dont read Chinese...this is the companies own tool and its totally freeeeeeeeeee

Just remember that it prompts in Chinese and on the left is "Deny" and on the right is "Allow"

Tried Zardamans excellent suggestion here....

.....but although I installed Google apps , the current OS kept closing them down so you still couldn't login & and it generating repeated errors so i uninstalled them in the end...on reflection it could be that I was "deny"ing privileges inadvertently, until i learnt a bit of Chinese.....anyway

Read an article which suggested using "Root Explorer" to install ONLY the 5 apps below

OneTime Initializer.apk

GoogleLoginService.apk

Google Services Framework.apk

Setup Wizard.apk

Gmail.apk

directly into root\systems\apps folder

Restart you phone - login to Gmail - done!

now install any/all of the other google apps including Playstore (this is the app that crashes the system if you install it before Gmail) just by running the apk file

I have:

Google playstore (sometimes called Phonesky.apk)

G+

ContactSyncAdaptor

CalendarSyncAdaptor

Chrome

Play movies

Google music

All working fine now

Yaaaaaaaaaaayyyyyyyyyyyyyy!!!!!!!!!!!