What protection in employment law do volunteers in charities have regarding bullying and unfair treatment?

I am a volunteer working for the Royal British Legion in Spain and am having problems with bullying harrassment and abuse of the complaints procedures. What rights do Ihave under EU, UK or Spanish law.

Phone ACAS on 08457 47 47 47
There are several 'affecting' issues. One is that this a British based organisation and on several levels are bound by different countries laws. Also you do not say which country you are indigenous to...but no-one - volunteer or otherwise - should be subjected to bullying and harrassment.
Ironically, Charities have the worst reputation for abusing staff and the problem with most is that the people who hold the senior (and paid) positions are often unqualified to.
Don't put up with it. Keep going until you get the response that you need. Blow the whistle if you have to.

i imagine that since you are not paid there are no rights as you are not an employee

If you are not paid then no employment rights other than health & safety and public liability insurance (I suspect). You do the work for charity and therefore you have the right to remove your labour at any time you wish. If it is a colleauge (you do not make this clear) who is behaving badly towards you then you can complain to the UK RBL head office. You could always complain to the Charities Commision (UK Government) asking them to intervene ... quite frankly I really dont think it worth the bother and I suggest you stop working with them and offer your services to other well deserving organisations.

Most of the Charities in the UK have codes of conduct, and written practises regarding Bullying, Child Labour, Harassment etc.

Get a copy of these first and use that. There may be some contacts higher up the tree you can deal with without going though the normal procedures.