For film related courses, English (either lang or lit or the combined lit-lang course) might be more relevant a bit in terms of textual analysis (for the lit options) or writing (for the lang options). Maths isn't really relevant to either interior design or film related courses intrinsically. However maths might give you some more options outside of those areas, and if you wanted to go into e.g. VFX for film, then having some maths background might be helpful (or even required, possibly, if the course is very computer science-y).
Do consider what your strengths and interests/preferences are though. If you are very weak at one of the subjects and/or really hate doing it, there is no point taking it to A-level because you will probably just badly in the subject and get poorer grades than you would doing another subject you prefer more. Also in general both subjects are only formally required for courses that contain a lot of that type of work i.e. literature based courses for English lit, which contain a lot of literary analysis, or STEM courses where you'll be doing maths day in and day out, for A-level Maths. Thus there isn't any point taking some subject to give you "more options" if those options would be ones you wouldn't want to (or would be unable to) do practically!