MAN-LHR-CPT. DUR-LHR-MAN

Hi all,

I am planning the above trip, o/bound in first, i/bound in club world using a companion voucher. As this is an open jaw ticket, will I need to call BA twice to secure these seats (if available) @-355 or can I book the o/bound tickets on-line then just call to add the DUR-LHR-MAN? Does one companion voucher cover this or do you need two? Sorry if this has already been answered elsewhere.

Thanks :-)