Ask HN: Scared to disclose business idea, bad previous experiences

I am working on an innovative form of online bingo, to do this I need to partner with a 'white label provider' who will give me the regulatory licenses I need to run my operation. They also often provide e-commerce and banking services and marketing.

Most while label providers also run their own gaming services in direct competition to my future business. However to begin a relationship with them I have to disclose screenshots or a video of my design.

I am really worried about this because in the past a business idea was stolen from me, the perpetrator used my idea to create a shell webpage, with alongside some dubious claims about having many clients for their product (which wasn't in reality developed) won £5,000 at a startup competition.

So far with some preliminary discussion one white label provider has suggested buying the idea from me (I have disclosed little information about the innovation itself) and conducting the development themselves. Am I going to be fleeced again?