Hi @aplackett 
Thanks for your question. Enter all the data including source country code and Box 135 foreign income from this USA into the T5013 slip.  Add a seperate T5013 slip for BMU and only enter the Box135 and BMU country code amount on this second T5013.  (ie you have to enter two T5013 slips if you have to report Box 135 income from two countries. The amounts will then properly fill T2209 giving you the proper breakdown of foreign income by country.