I usggest you phone or email the highways authroity or whatever they're called these days for confirmation of whether the M25 was closed or not. I had a similar case a couple of years ago and I done what I suggested. The road had been closed but the diversion signs wre rather sparse in placed. TfL agreed to waive the charge on that occasion. You never know, you may just be lucky by doing that.
Edited to add that Cattlegate Lane crosses the ULEZ barrier where it passes over the M25, the boundary follows the inner edge of the M25 most of the way between j 23 and j 25.
A closer look on GSV appears to show the ULEZ sign ar 90 degrees to the main carriageway, not very helpful for car drivers!https://www.google.co.uk/maps/place/Cattlegate+Rd/@51.6855559,-0.1136458,3a,15y,90h,83.66t/data=!3m7!1e1!3m5!1sa-gLypCigq_BBghWZZoH1Q!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D6.343201750430808%26panoid%3Da-gLypCigq_BBghWZZoH1Q%26yaw%3D90!7i16384!8i8192!4m6!3m5!1s0x4876220e8e5e7401:0x351f837f124e1ab5!8m2!3d51.6886724!4d-0.117781!16s%2Fg%2F1tv23n1r?entry=ttu&g_ep=EgoyMDI1MTEwNC4xIKXMDSoASAFQAw%3D%3D