Time for a slightly belated update.
The chassis went together quite easily although I'm a little puzzled over the two square brass frame spacers (and fixing countersunk screws) that are supplied - or I've completely mistaken their purpose. I fixed the two spacers in the only holes that I could see they would go and added the bearings, axles and wheels. The chassis free-wheeled nicely along my 2 yard long straight test track. I then added the end plates as can be seen in the above image but they were wider than the brass spacers and I could only keep the two frames parallel by loosening the screws on the brass spacers. Subsequently and because it was in the way of the "springing" that I have had it suggested that I could add, I replaced one of the spacers with a piece of code 75 rail cut to size and soldered to the inner faces of the two frames.
Spot the difference in the above two images!
I read the instructions for the kit when I opened the box and I've been re-reading/following them as I've gone along.
When it came time to assemble the coupling rods I looked at several photos that I've been sent/shown and decided which end of the frames was at the front of the loco. I made the coupling rods up accordingly - see the first image.
I'd opened the holes to 2.5mm and fitted both sides and the frame still rolled nicely.
For some reason I went looking at something else in the instructions and happened upon the drawing showing which way the motor should be fitted. Here I noticed that I'd assembled the coupling rods back to front. Much swearing ! ! !
I was slightly tempted to leave well alone but decided that wouldn't be right so I re-orientated the coupling rods with the aid of a 2.5mm drill slightly oiled so nothing would solder to it and pushed it in a hole on a piece of wood. I then slid the various parts of the rods over the drill, lined them up and re-soldered. The result is shown in the lower image.