Tonight after work I checked approx. 40 boxes in the first section of wood and once again as per last year, signs of delayed incubation and / or delayed laying mid clutch. The section I checked, I am totally convinced that this area is a couple of degrees colder than other areas being slightly higher and more exposed. I think next season I may try an experiment with thermometers at either end and in the middle.
Some slightly better news - bagged my second Wren nest record tonight, 2 eggs.