I am not in any way encouraging you to take matters further (sometimes it's just better for one own's sanity to move on and remember there's bigger things in life than getting Avios for stuff) but in my view, announcing before take-off that IFE is not functioning does not make it any better (unless you were offered a different flight or so - which I cannot imagine). IFE is part of the service offering and non-functioning mid-flight or from the outset (with announcement) shouldn't be treated differently.