Yesterday I got an email inviting me to register to get the vaccine. all perfectly genuine.
I clicked the link to get started and it was all downhill from there. I've lost track of the exact path I followed to total confusion and frustration, but basically it wanted me to "reset my password" (which I'd never set before). I created a password which seemed to be accepted, but when I tried to login using the userid they had supplied it said one or the other was not valid.
I closed the browser and tried the link again in case it need to be refreshed. Still didn't work. I clicked a sort of home button top left and got taken to page where I was asked for my Microsoft account. WTF? Being a compliant sort of a body I tried that and got taken down another rabbit hole where I ended up being told to contact the administrator because I was unknown in that domain, i.e. I was somehow behind the scenes the in covid application system itself. Now if I try the signon link again I just a page saying "password reset error" with nowhere to go.

At that point I thought I'd try calling the provided 0800 number. First time I was told they were overloaded and to try again later. I've since tried three or four times, and have just been left on hold with the most appalling music interrupted by patronising messages about why the vaccine is safe. Each time I have had to hang up because of an external interruption or the battery on my cordless handset has died.

I'll have another go on Monday.