Here are the sentences with "a" or "an" inserted where necessary:

1. My neighbour is **a** photographer; let's ask him for **some** advice about colour films.
2. A: We had **fish** and **chips** for **lunch**.
B: That doesn't sound **like** a very interesting lunch.
3. I had **a** very bad night; I didn't sleep **a** wink.
4. He is **a** vegetarian; you won't get **any** meat at his house. He'll give you **a** nut cutlet. Last time I had **a** nut cutlet, I had **some** indigestion.
5. **A** travel agent would give you **some** information about **the** hotels.

Note: "some" and "the" were used to make the sentences more coherent, though the prompts only requested "a" or "an".