I would be more inclined to say Satin considering the darker, glossier head and the corners of the breast with the wings also appear to be decurved rather than right angled in Leaden. Given that it is a rather unusual location for both, it seems more likely for a Satin migrating.
Hi Luke, thank you very much we really weren't sure and looked at so many photos and figured we would go for the safer option and if not an expert would decide. So thank you again, very pleased to have a Satin Flycatcher there. Thanks, your time and efforts are greatly appreciated.