@regcallum, as said in the ModMii guide, access priiloader by powering off the Wii then powering it back on and holding reset while it's booting. It can't find any hacks for your system menu because priiloader hacks don't exist for 3.3E Wii's (which is SM v354). So either you are not following a ModMii guide or you are not following it properly, because the only options ModMii gives u is to finish on SM v4.1, 4.2 or 4.3 (all of which have hacks for them, unlike 3.3).
I am truly at a loss at what you are doing (or rather what you are not doing), copy and paste the guide u supposedly followed in a spoiler and I can try to figure out what steps you skipped. I can tell you that at very least you did not install a 4.1 (or 4.2 or 4.3) system menu wad, and you didn't read how to access priiloader... so from my perspective, this is a classic case of someone having problems because they aren't following instructions. I'm not trying to be harsh or anything... but common...
Anyways, I suspect when you went to install all the wads, one or some of them didn't install properly, namely the system menu wad (MMM blocked u from installing it before installing the SM IOS), but you were supposed to make sure they all installed properly, and it would have worked the second time u tried to install that system menu since it would have installed the system menu IOS during your first attempt to install all the wads.
Good luck.