Finally got around to checking this out.
Just a quick view of 'cfdisk' (run as admin user) on my upgraded system
reveals (for /dev/sda)
sda1 285M (start 2048) [ext4]
sda2 7.86G Linux file system - raid_member (tagged CORE)
sda3 1.96G Linux File System - raid_member (tagged SWAP)
sda4 1.8T Linux file system - raid_member (tagged USER)
sda5 1.8T Linux file system - raid_member (tagged USER)
Free Space 839.5K
Apart from "Free Space" all partitions are contiguous (ie no space between them).
How I managed to achieve this using the installation package (.ins) rather than the update package (.bz2) on a existing system is unknown, but does open up some questions for support.