Runway change, a question of rules or etiquette?
The scenario: unlicensed aerodrome with intersecting runways and different circuit patterns for each. Training aircraft doing circuits on cross-wind runway, no other traffic in circuit or expeected. I wish to do one circuit to check some engine maintenance, but require the use of an into-wind runway. I chose to wait until the training aircraft had completed its operations, but it took long enough that I wondered what the position is re rules and/or etiquette in cases where this wouldn't have been an option (e.g. any additional traffic would probably have just prolonged the use of the cross-wind runway)?
As an extension of this, what is the position if returning to land and requiring a different runway from the currently in-use runway, where the waiting option is not practical?