Thank you both for your replies - this is really helpful.
Whopity - In that case, can a "regular" FI (not IRI) act as the instructor for these 10 hours? i.e. If I disregard the 5 hours I did during my PPL, I can utilise a non-IRI FI-holder to instruct me on the syllabus for everything in Exercise 19 and beyond.
mykul10 - Good point about quality over quantity! I was dreading revisiting all this stuff but running through some of the basics on the weekend I realised how much fun it is.