One of the anomalies of the BA booking system is that if you book a Club World with connection to a domestic BA, then the domestic gets booked in J if you are transiting via LHR thereby giving you lounge access, but if you buy a club world into gatwick with a domestic transfer via LHR after having got the bus LGW-LHR all on one PNR, you don't get lounge access at LHR at all.