Lg optimus L 70 system update won't work
If you have an SD card slot . Shove a 2gb+ card in there and point it to download to the SD card. You can use chrome or some other browser that will let you change  download location for every download. Only if this does not work - you can try increasing the space in /system
/System and /mnt/sdcard1 these are different partitions.Try clearing the /system partition by moving some apps that do not appear to be needed system apps. This can be done using Link2SD app. You have to be very choosy- if you select some vital app and make it non system it can be a problem.