After a quick mess around with the Electron I noticed what looked like composite out for a video output, but when it was plugged in to my tv only output black and white. At the same time on Mark Fixes Stuff Facebook group there was a post by someone else who was repairing his Electron and then modding the composite out for colour. As it turned out, Mark Fixes Stuff also has a video of the mod which I will link at the end of this post.
The mod involves linking across two pads on the board which are already there but not linked at LK4 as in this picture.
I cleaned out the holes and soldered in a wire link as below
Refitted the board and assembled the case and now have full colour composite video output on the Electron. And here’s the video how to from Mark https://youtu.be/oCUzgJPbUBI