Reporting back from using T5 North lounge today 05.30 - 08.30: lounge was as clean as ever & BA staff as nice as ever, and food still good (no complaints whatsoever on that front from me), but magazines were entirely HighLife / Elite Traveller etc with the exception of one Caribbean magazine, strangely from autumn, and a single copy of 'Hello' magazine.
So, sorry, magazine supply has definitely decreased over the last few months as far as I can see.