Looking forward to Al explaining/apologising/squirming for his hypochondria diagnosis of Valerie. Even more looking forward to Niamh being understanding and more importantly supportive to him in his hour of need!
What's worse is the way people made Valerie feel like she was being paranoid about being unwell, even though she knew in her very being that something was not right. She almost didn't even go to her GP thanks to people like Al not taking her seriously. Imagine if she had left it another few weeks until she became more obviously ill? Al is pretty lucky that Valerie did see someone else after all because his misdiagnosis could have resulted in her cancer not being discovered until it was more advanced and perhaps less treatable.
I can't really see Niamh throwing this back in his face though. If we see any reactions to Al's mistake next week, like you say, she'll probably be understanding and supportive.
We're on Gallifrey. Death is Time Lord for man flu!