Originally Posted by
jerrykenber
Thanks for the replies - much appreciated. I assume therefore that this process only works when there is availability in 'I' on both 'long haul' segments.
No, not at all.
Most fares are combinable on a "half round trip" basis, e.g. half the I class return fare + half the higher return fare.
So I class one way and J/C/D the other is perfectly feasible if that's all there is available and you're happy to pay. (But, you can't use half a round-trip fare for a one-way journey.)
fwiw, I believe the short EU segments book into J anyway.
hth