Hi Chipsodg
Are you referring to your return leg from LAS to LON?
Quite often on overnight flights up front passengers are asked if they want waking for breakfast since many (if not most) premium passengers do try to sleep on an overnight flight; hence it is a fair request. Simply saying no may have given the impression that you didn't want it and IIRC the LAS flight lands into LHR after the arrivals lounge has closed.
At least you did eventually ask for it, and I hope you got some. On balance I don't believe you have any grounds for a complaint. You were able to ask for breakfast, and whilst the crew member could possibly have been more tactful in your view, it is a good learn for when you next enjoy spending your Avios, and in itself an unfortunate misunderstanding.
Other than that I hope you got to enjoy the flights and LAS itself.

Am off to Brazil early next year so I'll ensure I am very clear about breakfast, though fortunately the flight is due to land back in time to enjoy the Arrivals Lounge at LHR so breakfast on board will not be required (unless we are very delayed).