I am resurrecting this old thread as I am about to fit Nav lights on by 50ft NB.
Blackrose - how have your lights worked out? Have you had to use them? More importantly (from my point of view) have they been seen, inspected, approved or disapproved by any lock keepers, river police or any other authority that might be interested in whether or not they comply?
A couple of points of my own. I have come to Narrowboating after 30 years of offshore sailing, many hours of which have been overnight. A tricolour is indeed a light designed specifically for sailing yachts. It sits at the top of the mast and shows red and green forward and white aft: that is all you need when sailing. Having it at the top of the mast means it is well clear of the waves and cannot be obscured by the sails. There is also no chance of the stern sector being blocked by the helm - it is way way above you.
I have read and re-read the relevant Collision Regulations including Annex 1 which gives lots of technical requirements. So long as the vessel is less than 20 metres ( a bit less then 66ft) in length (which mine is) you can combine the side lights into a single lantern on the mid-line which is what you have done. Sidelights can be anywhere along the length of the boat. The forward-facing 'masthead light' (always called the steaming light in sailing circles as it indicates you are under power) has to be forward of the mid-line. Having the side lights and the steaming light on a single mast somewhere forward of the mid-line thus satisfies all requirements. However, Annex I paragraph 2c says the masthead light must be 2.5 metres above the gunwale and paragraph 2h says there must be a metre vertical spacing between the side lights and the masthead light. It is on these vertical spacings that your mast is probably technically incorrect.
The point of my post is to ask the question - does it matter? It would need a mast 1.5 to 2 metres long to comply with these vertical spacings which would be a pain especially when approaching a bridge. I would like to produce my mast much like yours. Knowing whether or not it has served you well would be of great comfort to me.