Thank you for your reply. Very much appreciated.
This may simply be my lack of understanding of 90mm lenses but here goes:
If I put the XF 27mm on the camera and prepare a shot, the white indicator, as you say, shows the distance from the sensor to the area in focus. As I increase or decrease the aperture the blue bars either side of the white indicator move dramatically (showing the area in focus changing size). However when I put the XF 90mm on the camera and change the aperture the blue bars show a negligible difference between f2 and f16 at all distances. (I say all but i mean the ashtray, my gate post, the building across the street, and the tower block in the distance)