From the video I'd say that was normal for a car that you are just randomly revving. How hot did you let the engine get when you checked the expansion tank? Buy a new cap from Toyotas for a start and check the expansion pipe actually sits in water in the bottom of the expansion bottle and check the pipe doesn't have any holes in it. Also when you fill it up with water let the engine heat up with no rad cap on and run like this for a while to get all the air out and make sure the rad is always full to the top of the neck until you put the cap back on.
I ran the engine for a good 20-30 minutes with plenty of revving in between. I could only get the temp gauge to read just below half. There was an amber light on dash 'oil can with wiggly line under it' (very technical I am! haha). Definitely needs a good service and new oil, filter, air filter etc as well as wiping off all the rotting plums all over the body (was stuck under a plum tree!)
Sound promising and will def give it a go. Rad definitely new as far too shiny to be old! Rad cap has Japanese-esque writing on in but supposed could be a copy. It's been sat for months so not really reasonable to expect a clean exhaust pre-service I suppose.
I really do think this could be one of those simple cheap Eureka issues and throwing cash at it could be unnecessary. I'm tempted to rip the coolant system apart at the weekend. The fact that the heaters are blowing cold could mean something.....i hope!