This morning, quite unexpectedly, I received a text from Lambeth GPs Federation inviting me to have my 3rd dose/booster (both terms were used in the lengthy message), and I was able to make an appointment online for tomorrow afternoon. I hadn't given the idea of a booster much thought, but I'm certainly not going to turn one down even though I'll have to travel 150 miles to get it.
It might just be a glitch, though, as a month ago they sent me a reminder that I hadn't yet been vaccinated, only to send another text a few hours later apologising for the first one...