I can confirm good-will handling with a B2B ticket from an experience last year. We were in the LHR lounge waiting for our LHR-INV with a B2B connection INV-LHR-HEL... LHR-INV was delayed and so was INV-LHR with no chance to catch the LHR-HEL. The agent in the gold lounge changed our tickets and we were allowed to start our journey from LHR without the need to fly the INV route. Hope this helps.