Whereas if your student flies a circuit, lands, shuts down and comes in for another brief before repeating the exercise, that'd clearly be fine. Even if he did that 4 times a day for a week.....
A flight is a flight. That is an event lasting from chocks-away to chocks-under and as briefed by the supervising FI. For the CAA to assert that the Q X-C is not 3 separate flights is very much open to question. On what basis have they made this statement? Because they are, as is so often the case, talking total bolleaux.
How long would there need to be between the 'out' and 'return' portions of a solo landaway for it to count as 2 flights? An hour? A day? A week? A month......??