Casinomeister is not a UKGC licensed arbitrator, but they are certified by the chartered Institute of arbitrators: this post explains everything https://www.casinomeister.com/player-arbitration-pab/

Thepogg is a UKGC Accredited Alternative Dispute Resolution Service https://thepogg.com/ukgc-accredited-alternative-dispute-resolution-service/
and interestingly askgamblers have applied for accreditation, but I don't know if they've got it yet ref https://www.askgamblers.com/gambling-news/industry/askgamblers-to-be-the-alternative-dispute-resolution-provider/

For Oshi, we use AskGamblers as our primary dispute resolution service. The reason we do that is partly by circumstance.
AskGamblers rank very highly on Oshi key phrases on Google, so they ended up with the largest number of player reviews of any affiliate. Since they already had an active arbitration service  it made sense to ask people (as a last resort) to issue their complaints to askgamblers.

Askgamblers is one of the main places people go to check us out. So there is a great motivation to sort out issues that end up on askgamblers.

The same applies here i.e. if somebody is unhappy, they will use this arena to vent their frustrations. So if you read through some of the old threads, you'll see how we've dealt with difficult customer issues.

With https://game-protect.com/ , it's great to see other people getting into this arena. IMHO it's a healthy to keep operators in check.