The light bar and PCB for the O gauge GWR autocoach was surprisingly easy to fit. The only difficulty I had was removing and replacing the roof, since the clips that hold it on were a tight fit.
However, the lightbar parts are very easy to fit and since the pickups are already wired into the coach it is a simple matter to connect it all up. I used a Dapol Imperium 3 decoder. The whole job only took a few minutes. It worked first time.