Suggested answer:
(1) Example of countable hair:
If it did you might find a hair or some biological evidence that I'd actually worn...
Example of countable iron:
...with the bed in the corner cool and accommodating, and an iron and an ironing board against the wall...
Example of countable work:
Much as I love the works of J. R. R. Tolkien, I refuse to call any dog Bilbo Baggins...
(2) Example of uncountable hair:
...she's got beautiful hair.
Example of uncountable iron:
...there were mineral deposits, which yielded some iron and copper...
Example of uncountable work:
The man who was looking for work shook his head slowly before them all.
(3) Countable hair has the meaning of strands of hair, while uncountable hair typically means all of someone's hair together.
Countable iron typically has the meaning of "a household device usually with a flat metal base that is heated to smooth, finish, or press" (cf. Merriam-Webster Online Dictionary). Uncountable iron is a metal; "a heavy malleable ductile magnetic silver-white metallic element that readily rusts in moist air" (cf. Merriam-Webster).
Finally, countable work typically refers to a work of art (or something that has been done or made as a result of an effort), while uncountable work refers to work in general (or the physical and mental aspect of working).
Read about countable and uncountable nouns here and here
Terminology: countable noun, uncountable noun