Derfred
You wrote
[quote, I hate to break it to you but the autopilot is not going to give you a pitch attitude. It's going to pitch for whatever pitch it thinks is necessary to maintain what it thinks is your altitude. Your altitude comes from the same air data computer that is giving you unreliable airspeed.][/quote]
Slightly patronising tone but I will overlook it. If you are in a 777 simulator in cruise and a pitot or pitots block but the altimeters remain working normally the autopilot will remain engaged and will maintain the FL. That is the situation I was referrring to. If the autopilot disengages and the aircraft goes into a climb or descent with confusing instrument indications then of course I will do the unreliable airspeed checklist.
Good posts above from Monarchman and rblykyv and 8che who I believe have a better understanding of the spirit of the QRH.