Azure website returns 404 error after adding custom domain
The tried and tested method of going to bed and having another look in the morning seemed to work for me;) (Which means it turns out to be my own stupidity)
I had only added 'mydomain.com' in the azure portal and needed to add 'www.mydomain.com' as well.
I could swear that I saw some help text in the portal saying that domains should be input in that format though. Oh well never mind. I hope this helps someone else with the same error.