Liam,
Sony’s transfer software will combine the two parts into one file. You need to mount both cards (or add both BPAV folders you’ve moved to hard drive as sources) and use the transfer app to export the complete clip.
From Sony’s XDCAM Transfer User Guide:
“When the selected clip is in XDCAM EX format, and has
been split within a single SxS memory card because of file
system limitations, or when it has been split and recorded
across multiple SxS memory cards, the smaller clips into
which the original clip is split are called “child clips” in
this help. In XDCAM Transfer, these child clips are
displayed as subclips and can be handled in the same way
as subclips (except that they cannot be deleted)”
Hope that helps,
Zak