“I was going to do the washing, but we would run out of washing powder.” Shouldn't this be “but I thought we would”?
The question is about “the future seen from the past” from my grammar book.
The consideration of "the future seen from the past" isn't effected by the inclusion of a phrase indicating someone's mental contemplations. When standing alone, the clause "we would run out of washing powder" is an assertion: a positive statement given without corroborating fact. You can add, "I thought," making a speculative statement: conjectural thought. You can add, "I concluded," making a deductive statement: a conclusion based upon knowledge. You can also add "he thought" or "she concluded," or "they asserted." None of these affect the combined tenses used when speaking in the present of things that occurred in the past and involve something that would happen in what was yet the future at that time: you or someone else can be assertive or speculative or contemplative or thoughtful or deductive in a past event that involves something yet to happen in the future at that time.
To illustrate, imagine you are talking in 2011 about something that happened in 2009 and involved an event yet to occur in 2010. You can add assertion or speculation or anything else and nothing regarding the tense will be affected because all parts relayed in your 2011 communication already happened in the past. This imaginary illustration also explains why you can know that the future element did happen when you say something like, "In April, they left Edinburgh on Tuesday expecting they would arrive in Amsterdam on Wednesday." You can know they arrived because both parts of the sentence are now in the past (unless someone adds, "But catastrophe struck!"): You are speaking from your present vantage point (perhaps July?) about two things that happened in the past in April, though the second part was in the future (Wednesday) when the first part occurred (Tuesday). In other words, after they left on Tuesday, Wednesday had not yet occurred and you are talking in the present about both that occurred sometime in the past.