I, personally, would be less comfortable with this, than with a 13A socket on the lighting circuit in the loft (which I have) - based on the increased likelihood of someone plugging a vacuum into a hallway socket (and just unplugging the wall wart for a few mins) - compared to in the loft.
That said, worst case scenario here, this happens, and the breaker/fuse operates - with nobody balancing precariously on joists.
In my opinion higher risk, but lower impact. I personally wouldn't do/advise it in the hallway - but of course it's your house/decision, so this is just my 2p.