Finally got back to this thread
Len, I havent thought about that as the car didnt have one when I got it. I will just run without it.
So I have finished!!!!! Car sat in the shed untouched for too long due to Uni and other commitments.
I made a new fan shroud and test fitted it (rolled it into shape using a round piece of firewood). It is an interference fit to the hole and was fitted from the inside of the car after the bubble was put back on.

Used some filler to make things smooth

And after the whole surface was primed and painted to protect if from water, I used high strength silaflex to attach the bubble. I left the spot weld holes in the bubble in an effort to make it look like factory spot welds once finished.
Once the bubble was on I used sikaflex to seal the entire inside seam between the firewall and the heater bubble. Then I ran a bead around the hole and pushed the shroud into place. I went crazy on the sikaflex as you can tell but nobody will see it in there and its doing the job.
Primed
And painted using a pressure pack I had made up
And here is the finished product


Colour is slightly off however with the bonnet on you cant really tell.
Pretty happy with the result, looks reasonable for a first try and does exactly what it was intended to do - stops the car leaking!
Cheers,
Ryan