Locked out of MacBook air, no recovery key!

Thanks Eric, in an eye roll moment, as I was following your instructions, I tried versions of the changed password that maybe I had typed wrongly and low and behold it worked! Although when I changed my log in password, it also changed my appleID password.? So I will call apple support (after I have backed up my computer!) and find out what's happening. Thank you for your time in anycase, much appreciated

Hi Eric, unfortunately I believe I need the old password to reset a new one? And at this point I cannot get passed the log in screen on my computer because my log in password (which I haven't changed) is no longer recognised. I shared my screen with Apple support this morning to change my Apple ID password. This seemed to work. But later when I tried to open and sign into my Mac as normal, suddenly my normal log in password was not recognised. Apple assured me that changing the Apple ID password would not usually affect the sign in password, but it seems on this occasion it did and they don't know why. Sadly apart from needing my computer for work, I also have work I need to access on the desktop. Apple senior tech support were on the phone with me for about two hours today to help me try and log in to my computer but no success so far. I wish they had warned me there was even a slight chance I could end up being locked out of my computer :( I will be following up with a formal complaint to Apple. In the meantime, any ideas for a plan B that doesn't involve wiping hard drive?

Hi Eric, yikes I just realised I didn't expand your answer! Thank you! It's late in the UK now so I will check if anything works tomorrow and will report back!