Thanks for the detail, and what I said before still applies. You may have a case for 600€ provided the delay to LHR-HEL wasn't caused by weather, ATC or other so-called extraordinary circumstances. BA is thereby the operating carrier, against whom the claim needs to be made, and I would suggest following the process outlined in the Dashboard thread on the topic. If you know that it wasn't weather/ATC/etc then perhaps go the CEDR route (and therefore you want a Deadlock Letter); if not consider the MCOL route until BA provides the relevant evidence. Your connection at HEL was short, but definitely do-able, so my suspicion is that Article 7 compensation won't be a guaranteed outcome. As for IDB, I don't think you have a claim there, since presumably HEL did not leave full, the reason for the re-route was in line with the requirement of the Regulation for airlines to minimise trouble and inconvenience to the passenger. But for the missed meeting the alternative service was quite a good option. You can still get Original Routing Credit for the missing TPs and Avios, by the way, though the JAL ticket will make that complex.