Just back and in answer to a few questions:

Route of LHR-MAD. Booked myself on ba.com in May. Outbound was a BA flight number operated by Iberia and return a BA flight operated by BA.

Weirdly, online check-in failed to work either way with a message saying to call to have the ticket re-issued and it took a bit of fiddling at each airport before getting our boarding cards.

Fare basis from checkmytrip is OGOBA2 (economy restricted). I don't know what that means in plain English, but I booked ages ago and so was on the cheap, 5tp earning tickets.

The thing is, when I booked, BA had reformed the fare options to the three: Basic; Plus and Plus Flex. I clearly wasn't on basic as we had a baggage allowance and could book seats for free as silvers but very perplexed as to what I actually bought!