Can NOT remove myself from the XBOX PREVIEW! XBOX support is going in circles...

Basically, I have had two faulty XB1X's in the UK from game.co.uk with both having HDMI/screen blinking issues. both were replaced with "new one's" and now I can't remove the new UI that's available to preview members (known as insiders) I have removed my
device (even though the new XB1X wasn't setup under the insider app, only the one old was and serials matched to the old one, not the new one) and now I'm stuck and can't get back to the old one (the old UI) ... why? it says if I leave I may need to do an
update... no update ever comes through... it tells me there's nothing available and automatic update check was never! I have tried everything, XBOX support are going in circles with me and suggested I posted here!

I have tried factory resetting... nope. tried updating offline... nope. tried removing my account/device from the insider app... nope!

It's really starting to annoy me! I want a device that works! not go faulty after two weeks of use!!!!!!!!!!!!!!!!!!!!!

I have a fear that the issues I am getting with my ONE X's are due to the fact they're on the insider build. it works for a while and then goes crazy with my HDMI showing no signal and/or screen going on/off!

I posted on /r/xboxone and I've been told public users who are not in the insider crew don't see the new UI... cool; but I don't want it, too!

Help, removing the insider app and account is broken!

:)