Thickens further... 66023 was showing as being at West Drayton ARC at 19:48; can't suss which working it went on though. So that may or may not rule that one out.
66106 - having come in from Ardingly late morning - was reported as still being at Acton at 18:35 though. So that's a distinct possibility for being there when you passed.
No further update on 66162's whereabouts (last report still in the morning at "Acton Loco Holding Sidings").
66177 was there too, but left to Dawley Loop at 16:22 so may have been before you were there?
So, trying to piece this together, looks like 66034/037/106 were almost definitely there, 66162 possibly, 66023 possibly not; and 66177 but only until 16:22.
66006/007/144/188 were there earlier in the day, but would appear to have left by the time you were there.
In summary, EWS 66s are common as muck and trying to work out which were there in a pretty busy yard with movements all day is somewhat tricky! :?
(Couple of red ones were possibly there too, plus 59/2s as well, but guessing if they were you got those.)