Can I just confirm the process/path for this...

The 'release notes' i.e. what you seen in ZCC System Updates for 11.3.1 state:

Do not deploy this update to Managed Devices and Satellites until all the Primary Servers have been upgraded to "Update for ZENworks 11 SP3 (11.3.1)".
This update has a pre-requisite of "Update for ZENworks (11 SP3)" for the Primary Servers and Satellites in your zone.
This update has a pre-requisite of "Update for ZCM (10.3.4)" for the Managed Devices in your zone.


However, the 11.3.1 readme states
You can directly deploy ZENworks 11.3.1 to Satellites and Managed devices that have
ZENworks 10.3.4, 11.0.0, 11.1.0, 11.2.0, 11.2.0 MU1, 11.2.0 MU2, 11.2.1, 11.2.1 MU1, 11.2.1 MU2,
11.2.2, 11.2.2 MU1, 11.2.2 MU2, 11.2.3a, 11.2.3a MU1, 11.2.4, 11.2.4 MU1, 11.3.0, 11.3.0a, Win 8.1
for 11.3.0, Win 8.1 for 11.3.0a or 11.3.0 FRU1 installed.

I'm hoping it's the latter... We won't get the upgrade window (i.e. zcm unavaialble) to cover the 11.2.4->11.3a->11.3.1 upgrade of the Primaries if we have to cover off all our satellites too....!