My ex wife has moved abroad and I have as well. My chiild will soon be 18 and going to university in his/her home country. Would a new order for support have to be from Canada or the countryhe /she now lives in (the UK) if she requests me to continue to pay while the child lives away at University or would the same court order now in effect continue?

The current order remains in effect until modified. Since both parents have moved from the current jurisdiction then jurisdiction resides with the are where the child resides.