Thanks for your lighting report, Colin.
On mirrors: I've used a helmet mirror for years. Current one is a "Third Eye", I think it is. There are quite a few on the market here in N America.
I've found no "ideal" solution to The Mirror Thing. Tried a couple of bar-end mirrors on my drops: these were sturdy, but never showed me the traffic behind me as well as the helmet mirrors. I also tried a mirror fitted to my left-hand brake lever (you peel back the hood to fix it in place.) ("Left-hand" brake, as we ride on the right here.) This gave me good rearward vision, whether riding on the drops or the hoods, but was forever getting knocked out of alignment, so I removed it.
Through all my experiments with other mirrors, I kept the helmet mirror. Now, that's the only one I use. They seem to be a bit more fragile, though the current ("third Eye"?) seems well enough made. The small mirror has to be readjusted fairly frequently, depending on where you place your helmet after you take it off, etc., etc., but that's not much of a bother.
One caution: I used to use a Bell mirror (I think it was) which had two ball-and-socket joints, one for the arm-to-helmet mount, and the other for the arm-to-mirror fixture. A good idea in principle, but the joints were made of plastic, and the arm-to-mirror fixture in particular wore out rather quickly--lasted no more than two seasons. Mind you, it only cost me $9.98, so what did I expect? More than two seasons is what I expected...
Hope this experience is useful -- good luck.