I have frequently seen both in BE.

In cases where the 're' part was not imported from Latin together with the word itself you can always use a hyphen (which in some cases is pretty advisable for reasons of clarity).
to represent (imported "en bloc")
to re-present = to present again

I always thought the general rule was that a hyphen is inserted to separate two vowels when combining 're' with a verb:
to re-enter the password
to re-evaluate the situation

However, LEO has
to reappraise
to reevaluate
to reenter
to reestablish

Then again, LEO also has
to re-enter
to re-establish

Well, might be that LEO tries to cover all possibilities. Google results appear to be somewhere around 2:1 in favour of the hyphen.

My dictionary doesn't give the word and I don't think I've heard it used. I think I would say 'use again' as in 'Dont throw that away it can be used again'. If the word exists,then there is the verb 'reuse' and the noun 'reuse',each pronounced differently,but which if either has a hyphen? Recycle comes fairly close in meaning and it has no hyphen (my slightly dated dictionary).

I've also seen both verb and noun (with or without a hyphen) frequently in BE, maybe also in AE. I am surprised JGMcI, that you never came across it (and even your dictionary does not have it.)

I am curious to know what the difference in Pronunciation between the noun and verb is? Is it merely the stress? 're-use (verb) and re-use (noun)

Another word which I have often seen with or without a hyphen is pre(-)requisite.

The old hyphen problem.

Not even the wise and educated English native speakers seem to have a rule on hyphenation and there are differences between BE and AE.

If I'm required to use British spelling, I check my Oxford (reuse in this case). For American spelling, I check the Webster's Collegiate (also reuse).

If the word doesn't appear in your dictionary, I'd use my intuition or make an educated guess. You might also ask a native speaker, but there are many who don't even take notice of hyphens. This is an area where there is not really a right or a wrong and not always consensus.

There has been quite a bit of discussion on this topic in the forum, but I'm afraid couldn't find the appropriate links. Too bad.

@Uho: There is a pronunciation difference: the verb re-use has a z sound; the noun re-use an s sound. I'm sure you'll find a phonetic explanation at m-w.