....and here comes the problem....

I have merged to HDR using Photomatix. I have not selected the 'source images are linear' button.
I have opened my EXRs along with the best exposure in Nuke to grade the EXR to match the exposure as best as I can.
But clearly something isn't quite right and sorry if this is off the original topic.
I've attached a screenshot from Nuke - this is using the sRGB viewer.
I've adjusted the offset of the EXR to match the source image. In this example there is a variance in illumination across the image, and I guess this is telling me that either my source image isn't sRGB, or I've not been successful increating a linear EXR.
Or neither of the above!

Any ideas?