No screw under double flush

[ahd123]

Hi I'm trying to remove the cistern lid, and the YouTube videos I am watching say that below the buttons there is a screw you unscrew. However my flush does not seem to have a screw that I can unscrew and I can not get the lid off for the life of me. Advice please!

 

[Wayners]

Two button push to flush yeah.
Either turn the chrome ring that surrounds the buttons to unscrew or leaver buttons out and there is screw under.
You don't have that style.
Looks to me like there is nothing there to stop lid coming off?

That chrome oval insert in picture don't pull out?

 

[oldbuffer]

Try unscrewing the outer off-white nylon collar at the centre of your picture.