Hi Sam
Sounds like you are in a tricky place: hope it works out.
At one level, these are legal questions, and you don’t say where you are living / working: like anyone else I guess, a standard disclaimer from me would suggest taking appropriate legal advice if you can afford it …
Having said that, both the USA and the UK, to the best of my knowledge (and I’m a producer, not a lawyer), vest the initial copyright and moral rights in creative works in the “producer” – in legalese rather than video terms, being the person or organisation which takes primary responsibility for organising the work.
If you acted just as editor, that’s not you. If you in fact organised the whole video, which is what I infer from your question, it is you.
Many video commissioning contracts will specify an assignment of all rights to the client on completion / payment; however many more do not, and many projects do not have much contract or purchace documentation setting them up. In those cases, the rights rest with the producer. If that’s you, you can, at least in legal theory, control the use of your material, both in preventing copying and also (in the UK and Europe at least – I don’t know about the USA) – in preventing changes which you / the authors deem “derogatory” – your moral rights in the production.
At another level, maybe you should contact the people you know at the voluntary agency and ask what’s going on: they may not know. If they do, it seems to me that you, at the very least, deserve to be in the frame to carry out any re-editing or packaging: this is work you created, in part at your own expense.
If it is to be taken away from your control now, I’d think you had a case for charging the full rate for the work that went into it, and seeing that your contributors are properly paid. Better still, you might want to make sure that the voluntary agency (and not the start-up company) now takes control of the material: nobody wants the start-up owning or assuming rights in your material, I imagine. You could arrange an assignment of all rights to the voluntary agency in return for an appropriate fee. And if you still want to help them you could advise them to insist on an appropriate assignment of all rights on completion, together with physical transfer of master material, so they won’t be held to ransom in the future for access to work that they will have paid for …. !!
Hope this helps, and all best.