These cars are funny little buggers when refilling
I have found it best to fill the radiator as best you can,using the water pump hose side of the radiator , then expansion tank when the engine is started keep rechecking
Remove the air escape tube that leads into the expansion tank as mentioned before its imperative that this pipe is cleared using an airline

Now once level remove the little air escape pipe from the radiator side,fix a length of transparent hose to it
Attach it to the open bonnet and feed it water via the hose and a tiny pushed in funnel
Watch in your amazement as the water goes in ( when filling the rad via the top hoses you can never truly fill it up to the top what was in the head goes in to the rad you get an air lock and an empty head almost ) do this before you start the car and after
So keep filling the little pipe when no more goes in and no bubbles come out your done
All filled up quickly and enough to feed the water pump( as there wasn't enough water in the rad in the first place !)before the heads get hot and over heat sending the gauges that are fixed in the head shooting up

It is important to have the bleed hole in the thermostat upwards. Or you will struggle to bleed the system.