Closing Laptop Lid removes ability to manage multiple monitors

[Graeme Gellatly]

Setup

Ubuntu 17.10
Dell 9370 connected to TB16 with 2 HD monitors - DP and HDMI
When laptop lid is closed do nothing.

Issue.
When laptop lid is open - the displays setting shows both monitors and am able to rearrange them (although it only shows 2, and not the 3rd).

When laptop lid is closed - displays settings behaves as though there is one monitor and there is no option to rearrange (both monitors are going, and identified as 1,2 on screen at the time)

This was working as expected last week, so not sure if recent update or anything.