FlyerTalk Evangelist and Ambassador: The British Airways Club
Join Date: Jun 2008
Location: Somewhere between 0 and 13,000 metres high
Programs: AF/KL Life Plat, BA GGL+GfL, ALL Diam, Hilton Diam, Marriott Gold, blablablah, etc
Posts: 33,120
I think it is implicit from the two answers above but just to make it even more explicit, no, BA will not extend the luggage allowance of one booking onto others with a lower allowance, so you need to book a fare with whatever allowed checked luggage you'll need.