Thanks for your message Riley, husband and I went to dog training on Sunday and learnt some more things (see my original Hello From UK, New Dog Owner With 16 week old Shih Tzu, here) for that.
I talked to the instructor after the class about the Premack Recall sheet I got two weeks ago, and ironed out any questions I had as I wasn't 100% sure on certain things and didn't want to start doing this with Riley in case we were doing it all wrong and made things worse between training class. Anyway, we now know what we're doing and so we're going to start the sheet soon... famous last words