Three nights running is hard to dismiss as a one-off isn't it. Most people get one weird sighting and convince themselves it was a coat rack or whatever, but three nights means something is clearly hanging around.
Post the footage mate, that's what we're all here for. Had something vaguely similar in my old place in Abingdon a few years back - never got it on camera properly though, typical. Always appeared at the end of the landing around 2-3am which apparently is peak activity time if you believe the theory about the veil being thinner then.
The hallway location is interesting as well. Doorways, corridors, transitional spaces - a lot of encounters seem to cluster around them rather than open rooms. Some researchers reckon they act as focal points for this kind of activity.
Anyway get that footage up, lets see what we're actually dealing with before everyone starts theorising. Could be brilliant could be a shadow from a passing car. Only one way to find out.