For LHR-MUC, the full compensation of EUR250 becomes due at 2 hours, so for LHR-MUC a 3 hour delay would create an entitlement to 100% of EUR250

If it was successfully argued that PHL-MUC should be counted ( though I think that BA's argument is sound ), then a 4 hour delay would be required for 100% of EUR600 to become due. For a period 3-4 hours, only 50% would be due = EUR300

I think that BA has decent grounds for its argument on EUR250 and wouldn't think it worth trying to push for the extra EUR50