OP, it is too bad that you missed your wedding, but I find it difficult to have too much sympathy for you. It seems that you planned to get married on another continent and planned to arrive the day before. IMHO this was very unwise. Often international routes have low frequency and a small delay can cause major problems downstream, let alone a major delay at the point of origin.

Travelling within NA, I always try to arrive at my destination the day before, and even then I've almost missed events (and this on higher frequency routes). A few years ago my mother-in-law was delayed 48 hours due to weather, and this was only on the 1.5 hour flight from YEG to YVR.

IMHO you played with fire and got burned. What would your level of anger have been if your outbound flight was delayed due to weather or had to divert due to a medical emergency, or some other reason beyond the control of the airline? In such a case you might have only received a 5% goodwill discount.

AC certainly owes you some sort of compensation as it was a business decision that caused the initial delay. That being said, I don't know how much more you can expect to receive. AC got you to LHR within 5 hours of the originally scheduled time, and the connecting airline had issues that further delayed your travel. It sucks that you missed your wedding, but I'd hate to see what airfares would be like if airlines accepted liability for every missed business meeting or special event that was missed due to tight scheduling.