Espada. Did you talk to AF and ask them to hold your return bookings? As I mentioned the network airlines use the sequential and complete rule to protect their pricing. In the case you related I cannot see where they would consider it to be suspicious, particularly if you were calling from the UK.
The IATA wording actually says something like "if you contact us in advance and advise you are unable to use a confirmed reservation due to force majure we will not cancel reservations for subsequent sectors ... (But as mentioned AF doesn't follow the IATA recommendation)
However a Reservations agent may not have been trained to apply sequential use rules with discretion.
If you were refused and since you are going to be asking for a refund of the taxes, why not ask AF to refund the entire amount explaining the circumstances that led to your inability to take the outbound sectors and their unwarranted refusal to allow you to use your confirmed return journey.