If you don't mind travelling a bit. I took my missus to Sheffield Arena on Thursday for hers, she happened to mention to the staff that we were surprised I hadn't been called and they said there are a few anomalies in the system so try online. I thought I'd give it a go...got in for the Arena a week on Monday, but there were no slots there for the follow up but loads available in Ponty and Wakefield, so booked for the second dose at Ponty Squash Club.
Had mine yesterday, feel absolutely fine, did wake up this morning feeling as though Dominik Werling had been using the top of my arm to practice is free kicks