Thanks again to all concerned - this has been (and continues to be) a learning experience for me, and I'm most grateful for the wisdom and advice offered here.
I'll contact Expedia and see what I can find out regards ticket breakdown, and will then post in the 261 main thread (with reference back here).
Final info from me on this, in response to a question a little up thread - I booked my ticket on 16th Apr for travel on 7th May.
Thanks again to everyone. I will be back in 261 thread in next few days...