Originally Posted by
zkzkz
I don't think BA will check your bag through back to London, I suppose there's no harm in asking though.
Unfortunately, this can't be done. A bag tag can't say LHR-DUB-LHR (or LHR-DUB-LHR-DFW or XXX-LHR-DUB-LHR or XXX-LHR-DUB-LHR-DFW).
It's not clear from the OP's posts whether the trip is starting at LHR. If so, then I agree that the obvious solution is to drop the bag at left luggage at T5, fly LHR-DUB-LHR, pick up the bag and take it to the LHR hotel. (It's a pity that LHR-DFW is on AA, otherwise the bag could have stayed at T5 left luggage overnight, which would have made things even simpler.)
However, if the OP is merely connecting at LHR from somewhere else immediately before flying LHR-DUB, then things are a little hairier.