The following people contributed to the creation of this thesis. I would like to thank Anthony Henderson, who supervised my Honours thesis and set me on the path on re-search by encouraging me to start a PhD, and also for his latex code. I would also like to thank David Easdown for giving me the opportunity to start a PhD topic with him. Most of all, to Alex Molev: I still vividly remember the 2nd year introduction to modern algebra exam you set, which caused me to take a one year hiatus from pure mathematics. No one would believe me when I told them I had started doing a PhD with you. But the truth is this. You taught symmetric functions with such vigour and enthusiasm, and I was hooked immediately. Thank you for your dedication and hard w...