@Andehh thanks for the detail. I appreciate your point and will take a more holistic view re air tightness etc.
@jfb, thanks for the suggestion. I will ask for this to be done. Although, I am now leaning more towards @Iceverge suggestion of a 350mm dig out.
@Iceverge, thank you so much for this. Anywhere we can save is very welcome, in addition to “less” work.
I’ll be back with an update.