great thanks! yes i just could not discern if there was an actual BA Policy so this has all been helpful to plan ahead knowing there is nothing official!
have never had this issue with an overnight at LHR before but as noted above i think at places like JFK there has been a crazy focus by AA on skiplagging which does not translate to normal things in LON like LHR/LGW/LCY or overnights and movement between the airports before continuing on the next day.