Hey thanks for your help,
Using the actual IP address of the WAN interfaces (as opposed to the interface name) in the dst-nat rules did the trick. Does seem odd though as the interface name method should in theory work as well you’d think but nonetheless happy with the outcome.
Also cleaned up my config considerably after doing more reading on Mikrotik, my new config is here if anyone else runs into the same issue and wants to review.
https://pastebin.com/PPz549nv