what type of visa should I apply for?

I have recently returned back to Canada after living in England for five months with my boyfriend who is a British Citizen and before I left he asked me to marry him. I am unsure of what visa to apply for. My friend and I plan to return to the UK to travel in Ireland and Scotland the first week of September and I'd like to have this figured out before then. Should I apply for a Fiance Visa? We don't plan on marrying in six months, but rather in a years time. Are there exceptions on a Fiance Visa? Or should i apply for a Work Holiday Visa which will allow me to work while we make wedding plans, and then apply for a Marriage Visa while in the UK? If anyone can help me through all of this confusion I'd truly be grateful.

Many Thanks. Juans