3. Use the Baseband fix by @dipesh1502.
Download and flash the following ZIP using CWM/TWRP/Philz.
Download it HERE
Thanks to @dipesh1502 for creating this Flashable ZIP.
4. Alternatively, I've created an FTF for Xperia SP C5302 variant having only Baseband (<1MB). You can download it from HERE.
Flash it using Flashtool.
BaseBand Fix.zip from step from above contains 2 folders (System and META-INF); What do you do with either this zip file or its contents. For sure it does not go into the firmwares folder (since it is not picked up by the flashtool). The same thing goes for the alternate method of step 4; placing that in the firmwares folder yields nothing - it is not listed in the flashtool thereafter. I have the latest version of the tool and also the version prior to that. Please say what I am doing wrong because obviously I am doing something crazy