Interesting thread, just catching up with it.
Re the rangers - I've been hiring in winter for the past 14 years, usually in December and February. I can't recall seeing a ranger although I suppose there might be some about. We've crossed Breydon every December and most years in February. We've also moored at Reedham numerous times. The quay is pretty much empty in winter which does make life easier I must admit. Might not be so good for novices though. I wonder what the rangers do in winter?