I did substantiate them adequately, you can google and confirm the companies house registration or whatever other info you doubt. Which is what exactly? Seems pretty clear cut.

The filing, the financial backing, or that this is what they do ?

Also, who appart from you can vouch for the reputation of the Twitter person?

First one is literally this guy

Professor David Miller is one of the world’s leading academic experts on Islamophobia, and also specialises in the analysis of state and corporate lobbying.

Until his recent sacking by the University of Bristol, which resulted from an outrageous censorship campaign led by the UK's Israel lobby, he taught political sociology. He also set up the UK’s lobbying watchdog, Spinwatch, which has tracked corporate power for 15 years. Spinwatch’s work has included investigations on the pharmaceutical lobby, the fossil fuel and fracking lobbies, as well as state lobbies that promote Islamophobia, such as those of Israel and the United Arab Emirates.

https://supportmiller.org/