I had that issue using the Edge browser. Switched to Chrome and it was okay. You might find in Chrome, it tells you that your email is already taken in which case go to the sign in option for existing customers and you should get in from there as the account has already been set up.
Thanks for the link. I usually buy the lapel badges from the shops each year as I lose so many poppies. I would expect that sellers on Brighton station might be given a supply of the Albion ones but as I have ordered four of the badges for the family, I don't think £3.99 is an issue.