Well the dock for my Surface Pro 4 has arrived, and my Windows Surface is now working with external displays again. Though it didn’t work at first: it turns out that my current display adapter was broken too. With a new adapter (mini-display port to VGA) and the dock all is well.
The new adapter does work intermittently with the direct display port on the surface, but the connection is wobbly and unreliable.
One big advantage of using the dock is that the adapter and VGA cable can then rest safely on the desk/lectern. So I can use my Surface on a laptop stand on a box (for extra height and better writing angle) without there being an issue of the weight of the VGA cable pulling on the adapter and indirectly on the mini display port connection.
Has anyone else had similar problems? I know that some people have abandoned writing with the Surface on a slope because of problems with the connector. Perhaps some good will come of my problems if it helps others in my situation!