I really feel for affiliates caught up in this scam.
I'd suggest affiliates should lodge a small claim procedures in the UK (I believe you don't need to be a UK resident, only have a UK postal address. A drop box/forwarder would surfice here).
Blacklisting is not effective these days. But, Social Media is. Especially when you name and shame the CEO, CFO and Board of Directors. Get active together, as one voice. Everyon using the same hash tags such as: #GalaAreCrooks, #LadbrokesAreCrooks.
Programs/casinos/sportbooks etc., don't seem to concerned about being Blacklisted these days. But, start targeting the upper management and board members, and associate these people with these scammy, criminal acts, and I'm sure is will yeild results
Get organised together
set a plan of action, and stick to it. Name and shame to upper management on Social Media.