As I mentioned in the review, although the Play Store come preinstalled in the ThL W3+ it was not working at all. So, as my first attempt to fix it I scoured online for an updated firmware. It wasn't easy as I do not speak/read Chinese but nonetheless I managed to find it. The main site appears to be thl.cc where you can check for latest firmware and support but everything is in Chinese. However the new firmware does not help as the Play store still wasn't working. So, the next step I tried was rooting the ThL and replaced/install the required Google apps. Guess what, it worked :).
The following steps show how to root the ThL W3+.
1) Download the USB drivers for MTK6577 here.
2) Download the UnlockRoot software here.
3) On your phone, go to Setting, Developer options and tick the USB debugging option.
4) Extract both the USB drivers and install UnlockRoot.
5) Connect the phone to your USB port. By now, windows will try to find the driver for the phone and will fail. So, open up your Device Manager (Click on Start button, type Run and then type devmgmt.msc and then enter).
6) There will be one item with a yellow tick on it named MTK65XX.... device. Right click on this and click Update Driver Software.
7) Point the wizard to the driver's folder you just downloaded. Make sure to tick the Always trust... option.
8) Open the UnlockRoot, click on Root and then select the ThL W3+ device.
9) If it asks you if you want to re-root just click Yes.
10) Now you device should be fully rooted! To check just look for a Superuser app on your menu. If there is one then you have successfully rooted your phone. Otherwise, comment on below for more help.
Fixing Play Store
Without rooting, you cannot get Play store or any other Google apps to work on the phone. This 'may' be due to all the other relevant services not being installed on the device. Follow the following steps to fix this.
1) Download Google Apps archive from here courtesy of CyanogenMod team.
2) Extract it and inside it go to system folder and copy the whole app folder to your phone.
3) Download ES File Explorer from here. Click on the first selection.
4) Install the ES File Explorer, open it, click on the options button on the phone (next to the home button) and click Settings.
5) Tick on Up to Root, Root Explorer and Mount File System.
6) Copy the app folder from step 2 and paste it to the system folder (overwrite the app folder).
7) Once done copying, open up the /system/app/ folder and install GoogleLoginService.apk, GoogleServicesFramework.apk and finally Vending.apk.
8) Reboot your device and voila, the Play store should be working now! If not, again do comment below.
PS: Here is a tutorial on how to update your phone's firmware.