On my Zetec I blanked the heating loop, but there is a separate thermostat bypass hose runnig from the stat housing to the water pump. The thermostat housing has 3 outlets: the 32 mm upper rad hose, the 19 mm bypass hose, and the 19 mm towards heating. I have the heating port blocked off. If your thermostat has any kind of a bypass besides the heating loop, you can try blocking it off and seeing if that works.
https://photos.app.goo.gl/kGMB25gAX8mZYHdH6