My view is that, for traffic joining 'straight in', 'final approach to land' starts once you are inside a point on 'final' where you might reasonably expect the 'base leg' traffic to be, or inside the actual position of base leg traffic, whichever is the closer.
That is a long version of what I meant. If you have a published traffic pattern, I would assume someone "on the published final line on the chart" to have right of way and somebody on 15nm "long final" definitely not. Isn't there a setting in the UK with something like 8nm long final, 4nm final, less 4nm short final?