A page calling itself "http://searchomepage.com/" has installed itself as default start page but is not showing in Add-ons. How do I uninstall it please?

I have tried resetting the home page in options a few times, run Avast which found nothing untoward, Malwarebytes which did find something called Secure VPN which installed itself at the same time as this homepage but Malwarebytes successfully uninstalled that but nothing works on the searchhome page.

Any advice gratefully received.