Just been through the same as you - missed the tier points because of short term schedule changes/cancellations over summer (withdrawal of a LGW-GVA service for 6 weeks).
Asked nicely and was rejected. Wrote nicely to head of Exec Club in response to the letter where they told me it was 'unfortunate' that I hadn't earned the tier points, sent it recorded delivery and haven't even had the courtesy of a response.
They're obviously not that desperate to keep Exec Club members so I wouldn't hold your breath