Thanks for the quick replies, comments/answers:

split the booking: I can do this but not sure if it will help as still a TA booking and I haven't yet been successful in UuA'ing a TA booking (others have). Also open jaw so not sure if that affects it. If I see availability show up then I will try to ring (and my colleague is also willing to UuA so we may work something out between us if this is the only option.) If it was a direct BA booking that would have helped regarding chances, IMO.

I CWS is right about the two boarding passes, unless I went to a check in desk and explained the situation and hope for some help in this regard. To be clear, I don't feel I am doing anything underhand here, simply realising that work won't book me in the class I wish to travel so for the outbound leg I wish to book a separate ticket and still fly that flight. I would happily forego the TP's (already gold for this year) obviously Avios would be good to help offset my outlay but not too concerned if I lose those as well. Just wish to fly a better class and not lose the inbound leg.

What made me think this may be possible is that is should be possible to book several seats, for example in Y if you really wanted privacy and a bit more space, if it was deep discount without having to pay for CW. So I feel it would be possible to book two seats (or three) in Y beside each other on a flight with only one person flying but how does that work in practical terms? (and in my case with two different classes on the same flight?)

Any other thoughts? Ideas?

I'll obviously try to upgrade at the airport if it comes to that, I would happily UuA if availability comes for CW and even for two and then work that out between my colleague and i (or split the booking). Just trying to think outside the box for how to fly the same flight out and not lose the return leg. (As CWS said, I could work around it if this was the inbound leg if needed.)

Ideas (with this further info?)