Hi Mahesh, and thank you for the quick reply. Ok, I understand and I have managed to partly resolve the issue by adding the default header image into the theme.
All of the featured images I am using are running full width of the site and they go in at 2w00px wide. You can see this on a sample page, for example:
http://s328332815.websitehome.co.uk/Clinicept-WP/contact/
The image I am now using on the Blog page by fixing the issue using your advice seems to be locked at 1200px wide. Is there something I can do to make that page also display the featured image or header image at 2200px wide? You can see the blog page at http://s328332815.websitehome.co.uk/Clinicept-WP/news-blog/
If you can let me know what to do here then I think I am finished and I can get this site put live 🙂
Thank you in advance 🙂