There were two problems - router setting and the domain name (managed by Go Daddy) was not pointing to the Plusnet IP address.
I tested access to the website yesterday afternoon and this morning: after the OP sorted their router, the site could be accessed by IP address but not via the URL. This morning the URL works.
Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.
