Hi Geoff,
I would suggest two things to you. As this is a nesting situation (with more than one bird and likely of both sexes) you should be able to get an idea of the range of sizes of these birds and thus, by virtue of that female BG & male CS are outside the size range of the other species, know from that. Also maybe you will have an opportunity to return and get a clearer idea and perhaps get more familiar yourself with them.
However, on face value, just from what shows on the photos which does not include size, (barring tricks or traps in the photos) these are certainly Brown Goshawks. The feet, the head shape, largish beak, rounded tail, all point to this.
Philip
