There is at least one "crew friendly" proper hotel that usually has a crew rate £51 (and can be cheaper if you pick the right day and look at their public rates...).
If the BA shuttle buses aren't running then remember (?) that the TfL red buses are free around the perimeter, as far as and including Hatton Cross/Harlington Corner.
But yes, food isn't cheap (then again there's M&S in T5), so £70 sounds reasonable .