This worked! I used gparted to extend the efi esp partition. It was 260mb so I’m extended it to 2GB.
My partitions look like this:
- EFI system partition - fat32: 2gb [WAS 260MB PRIOR]
- Microsoft reserved partition: 16mb
- Windows ntfs partition: 180gb
- Free space: 770gb
Restarting the qubes installer using the 4.3 installation media now works!
Post installation, my partitions look like this
- EFI system partition - fat32: 2gb
- Microsoft reserved partition: 16mb
- Windows ntfs partition: 180gb
- UNNAMED - ext4: 1gb
- UNNAMED - [Encrypted]: 770gb
Can i buy you a coffee 
?
Now I must figure out what went wrong with my previous installation…
I remember sys-USB was having issues mounting my external SSD. Previously, i had attached SSD to a disp and restored Qubes from it.
This is the error in get when trying to mount any media in sys-USB:
not authorized to perform operation (pollution authority not available and caller is not uid0)
Edit: this is a known issue. See here: Error during 4.3 upgrade
I have also noticed the pci device (ethernet) for the sys-net i restored from 4.2 does not exist! I had to resort for the default sys-net that Qubes 4.3 installed. This default sys-net had both wifi and ethernet pci devices which worked correctly.
Is it normal for pci devices to change names?
EDIT: added sysusb error code