Are they reliable...?

[aus9]

How are they at solving problems / customer care?

one word of caution here. GB customer support depends on how great the maker support is, not the other way around. And is true of all sellers.

My advice don't buy some cheap phone....that has no official roms at needrom.
That way you can use windows (EEK) and flashtools to hopefully recover from your mis-adventures

Ask them to confirm it only uses the following filesystems
ext4
vfat (fat)

we have a forum about buying phones so why not name the phone and link to it?

we may have members willing to share their experience of the phone tho may not have bought from GB?

good luck