Why didn't you choose the former 'Train Spotters Platform' in Finsbury Park itself.. That's where we used to stand -- you get a good long view there.. I have mentioned it before..
There was some confusion about which line it would come in on. It should have come in on platform 1 but was delayed at Peterborough (a signal failure I think, which was holding all the electric trains up as well) and ended up coming through on Platform 2.
Finsbury Park was very busy - so we just got as close as we could.
I think that 'train spotters platform' has been removed, Steve (I didn't know what it was, overlooking the bridge near the Oxford Road entrance, until you mentioned it).