They're not cancelling appts.
This has been in the planning stage for the last month or so.
We were actually told last week by someone locally managing vax that Monday 13th was a National roll out to all.
Gps will have paused routine asthma reviews for those will less serious asthma etc, routine thyroid tests etc. So letters won't have been sent out for appts. Those sorts of things can wait another month (I have both.)
Urgent cases of asthma will still be seen and treated. There's a huge number of Gp appts that are regular reviews. Those can be pushed back for a month to give out jabs.
There's also a lot of people eg pharmacists who were giving jabs and volunteering previously, working 12 hour shifts for free and others who've been specially trained, who are now going to volunteer.
My first jab was given to me by an army (no idea status.) the army have loads of medics who've been deployed everywhere.
I'd keep trying the booking (it was a bit crazy two weeks ago and I had to wait 5 mins) and look at council pages for walk ins. Locally they've been running for a week or so too.