Eerrrr!
The beta has only finished on the S21.
@Babayagaa has the Note 20. This beta is still running AFAIK. Well they may not be taking new people on I guess but if you have a CSC of BTU in the UK then you should be able to see the banner as shown above. Now, there have been some instances where devices purchased direct from Samsung do not have a CSC of BTU and I have a feeling that this has happened as the devices were booted up without a UK sim in them, this is only conjecture though based on previous discussions.
So check your CSC to make sure it's BTU and if so then clear Cache and Data on the Members app and or reboot to see if they helps. If you do not have a CSC of BTU then have a search on how to change it as long as you are a little technical.
Best of luck!