So here is the outcome so far.... went to MUC to change the ticket; paid change fee for the Z fare so routing is now MUC-FRA-Canada. Cancelled the economy ticket and actually had eu64 of the eu89 total refunded which was a good surprise!

I decided that the chance of going overweight and being charged was too much of a risk, and the change fee is not charged to me directly so won't hurt my pocket (whereas the overweight fee would)

I went to Aldi and Lidl this morning so the chocolate supply is quite replenished

As to why I did not originally book all in one ticket, I have been on a rather 'interesting' trip in the last month which has taken me to Mumbai, Goa, Delhi, Paris, Frankfurt, Munich before going home. I only squeezed in two days vacation to go back to Bayern before I leave again. The itinerary also changed a few times along the way.....