"coiner" - one who counterfeits coins. Not something we hear of much today, but in earlier times was a reasonably familiar sort of criminal.
"box-room" - a room in a house (usually a small room) which is just used for storing things, usually things that are not wanted very often. The collocation "box-room attic" is unusual, because these two words mean nearly the same thing. (Not quite, because a box-room could be anywhere in a house, not just under the roof).
"cistern": yes, it is still quite common for British houses to have a water-tank in the roof space - sometimes two (hot and cold). This was partly to provide a head of pressure for taps and showers, and partly to guard against interruptions in supply (and in the case of hot tanks, to provide a reservoir of heated water for when you needed it quickly, as in a bath).
There is not a literal tunnel, it is saying that between the tank and the sloping roof there is a long and narrow dark place (dark because it is behind the cistern).
"of course" is a parenthetical remark meaning "as you already know", or "as is obvious". It is much more common in speech than in writing, but of course this writing is meant to suggest somebody is speaking, and telling a story.
"For" says that the sentence is a reason or explanation of what precedes. So the meaning of "For of course he was thinking .. " is something like "(He was excited) because, as you probably realise, he was thinking ... "
"Running late" is an idiomatic phrase that means, essentially, "late" or "being late," with the caveat that "being late" is more a translation than a phrase that people use. The Oxford English Dictionary defines it as:
- "s. to run late : to be behind schedule. Similarly to run early, on time, etc."
For your example, you could write "He was late so he sent a new doctor to run my follow up appointment." What's different about that way of saying it is that "running late" conveys information about why the doctor was late. He had a prior appointment and it took longer than expected. Perhaps it would be even better to write "He was taking longer than expected with a previous patient so he sent a new doctor to run my follow up appointment."
If you tell someone you are "running late" there are a few important connotations. First, it is probably in reference to a meeting or scheduled appointment. Second, you could already be late or simply anticipating that you will be late. That would depend on the time the message is conveyed relative to the appointment or scheduled time.
You are correct that "to run" the follow up appointment means approximately "to deal with." However, just know that at least in the United States, you don't normally "run" an appointment. It's understood, but not common. You might run a meeting but usually you "have" an appointment. I would have written it as "he sent a new doctor to meet with me for my follow up appointment.
I would also point you to a discussion on WordReference.com about this phrase.
Best Answer
This is a common retail clothing term. The phrase "run small" in this context means that they tend to be smaller than most brands with the same label size.
Clothing sizes tend to depend on the brand. A pair of Levi jeans labeled as medium will most likely not be the same size as a pair of Wrangler jeans that are also labeled medium. When this occurs, the phrase "runs small" is used to express that Levi's jeans tend to be smaller than most brands with the same labeled size. "Runs large" also is also used in this way.