I never work out the value of one mile/Avios spent....I couldn't care less to be honest. I like the flexibility they offer more than the cost saving.
So with that in mind it would have to be the two LHR-EZE tickets in F I booked for my wife and I at short notice which allowed us to arrive here just in the nick of time to meet our container of belongings which had done the trip by land and sea in record time.
It was my first trip in F as well....a memorable experience.