thanks
so for LHR-IAD out 26 march and back on 2 apr i see
26 Mar
BA217 £1,587 (D) £7,882 (F)
BA293 £1,287 (I) £1,786 (A)
and if i select J
2 Apr
BA216 £1,036 (I) £1,535 (F)
BA292 £1,036 (I) £1,535 (A)
So choosing J on BA293 + BA292 I get a total of £2,321.
If I choose F on BA293 then when I get to the inbound screen I see
BA216 £1,311 (I) £1,535 (F)
BA292 £1,311 (I) £1,535 (A)
So they are more but still in I class, and it isn't selling class. Possibly fare incompatibility? If I look at fares for those dates it seems the J out and back is using fare LHX1C1Q4 for out and back, this is a first and business class special half roundtrip fare. Not sure which fares F out and J back is using, but clearly there is something going on when you combine F & J here.