Ambassador, British Airways; FlyerTalk Posting Legend
Join Date: Apr 2012
Location: Leeds, UK
Programs: BA GGL/CCR, GfL, HH Diamond
Posts: 43,363
Any free cancellation within 24 hours would be based on what avios.com allow. Certainly the BA cooling off period would be irrelevant for a booking made on avios.com.
Having a look at avios.com I can't immediately see any reference to a 24 hr free cancellation period.