OK thanks. Python scripts are beyond me so I guess I'll try a combination of software to achieve a result. Using other software I have found a value on the header:
DATE-AVG= '2015-07-14 T 09:26:31.967304111' / TAI date at middle of observation
which seems to correspond to the HSC site file finder. I've never used that value before as a guide but it seems the easiest way to proceed.
However that software cannot open the image but AIJ can, so I will use one with the other
Best get on the case!