There's plenty of the vaccine available and they'll throw it into the arms of anyone who's eligible - you're not risking taking it from somebody in greater need.
Anecdotage - boosted on Friday (Pfizer) as a walk-in, no queues, no side-effects other than a slightly sore arm on Saturday.
I couldn't book as an over 40 the other week. I'll wait since I'm already pretty isolated full time and there's other people could do with it sooner.