British word for...

Hi,

I'm looking for a translation of a Dutch/Flemish word. We call it "VZW (vereniging zonder winstoogmerk)" This is an organisation like a non-profit organisation. But is't smaller, raised by just few people.

In our case, we have a VZW Medical Failures. People can join the "VZW" en they write letters to the organisation where they describe the facts/failures that happend in the hospital. The goal is to recieve medical and juridical opinions from the "VZW".

Is there some kind of translation for this organisation?

Thanks!