Hi Ciaran,
I move my web site with Enterprise template on Joomla 3.7 from "http" to "https".
Here is: http://bit.ly/2pFqmrM - and the fonts are changed.
I don't succeed in finding the referals to change:

http://fonts.googleapis.com/css?family=Raleway:100,300,400
http://fonts.googleapis.com/css?family=Open+Sans:100,300,400
http://basehold.it/27

Also I don't understad if these rows will became so:

httpS://fonts.googleapis.com/css?family=Raleway:100,300,400
httpS://fonts.googleapis.com/css?family=Open+Sans:100,300,400
httpS://basehold.it/27

or (without http or https):
//http://fonts.googleapis.com/css?family=Raleway:100,300,400
//http://fonts.googleapis.com/css?family=Open+Sans:100,300,400
//http://basehold.it/27

I'll be grateful for your help.
Thank you very much
A nice weekend.
Andrew