Advice please. Flying Auckland, NZ - Toronto with just 3 hour stop in Vancouver. 20 hour flying time all-up and arriving Toronto 2 AM. Will just want to collapse into bed at nearest half decent airport hotel. Suggestions please for arrival night. Will make my way into proper accommodation nearer the city later next day after a good sleep. Much appreciated.

Can't help much on the hotel -- there are plenty of them and an on-line search should line up the prices. However, I wanted to point out that the direct rail link between the airport and downtown is now running. It goes to Union Station in the centre of downtown, where it is easy to transfer to Toronto's subway. https://www.upexpress.com/

Aha! Thanks for that. Maybe I could prop my eyes open with matchsticks and make a run for it into Downtown. Thanks for that.

I think the train stops at 1AM

If you make it to the train station, the HI Hostel (76 Church St.) is within walking distance. I don't know when they lock the doors for the night though.
http://www.hostellingtoronto.com/100/Rooms.hostel
It's been a few years since I was there but it was good then. Price includes breakfast.