Never been to that particular mill but I've poked around enough derelict industrial sites in my time to know they have a quality all their own. Something about the combination of confined spaces, strange acoustics, and the sheer weight of human suffering those places absorbed over the decades. People worked themselves half to death in those buildings.
What specifically are you getting at though? Sounds, apparitions, that heavy feeling like something's pressing down on your chest? I've had that last one in three separate locations and it never gets less unsettling no matter how many times you experience it.
Anyone local to Ashford who's actually been inside - I'd genuinely love to hear what you found. The textile mills up north have decent documentation but the Kent ones seem to fly under the radar completely which is a shame.