This isn't going to be a lengthy post as there is so much information on the Internet, instead, I'm posting some really useful links for bow tuning. I can't believe how much of a difference this had made to my shooting.
From the Coach's Manual at World Archery GB - this is definitely useful!
Merlin Archery Part 1 Review - shows adjusting Tiller and Brace Height etc.
Merlin Archery Part 2 - Twisting bow string, upping the poundage on your bow.
As I hadn't done any bow tuning at all, I did all of it in one go, starting with brace height, shooting bare shaft arrows and adjusting the plunger. All seems good at the moment, so just going to shoot and then review once I know a bit more.
Ps. I've now pushed my bow to 26 lbs (don't laugh!) and re-checked all my tuning - life is sweet.