Lighthouse Mizen head

This is better Paul. I know that it can be hard to judge from a computer screen but I would be inclined to go for a harder grade again. It is often better to go beyond what you think might be correct just to see what the result will be. I work with 8x10 RC paper to find the most suitable Filter Number before I commite to FB. I do like your shot by the way.

It's better. Some of the texture in the walls along the path is starting to come out. If this was printed using grade 3 filtration, I would tune in the highlights with this filter grade, burn in the bottom and top of the frame at 50% of the rest of the expsosure, and then give a Grade 5 exposure of about equal length.
Your lighthouse is now almost paper white. You need to work on your blacks.