Apologies if this is really obvious. I wish to book a lhr-gru return ticket (in WT+). For the return journey, I wish to start my journey in EZE (in club, for the TPs) and then proceed on from GRU to LHR on the return segment of the original ticket on the same plane. So I was thinking of buying a separate ticket for the EZE-GRU segment in club. But I was not sure if this is allowed- checking in for the EZE-GRU segment for the GRU-LHR segment in a different class.