Thanks Kage, it is set to Trusted.

Can't see anything in the hosts file that would affect your access to the router
The only thing I can think is that the firewall might be blocking it for some reason.
If you cannot reset any firewall rules then try disabling it or maybe uninstalling it just to test.
As I mentioned before sometimes disabling it doesn't always stop it affecting access.
You can always reinstall it if makes no difference

Update! Since our previous debate I have recently renegotiated with Sky and have now got a nice shiny new Sky Q router and am waiting for fibre connection on 8th June. However could not access the router and got same message as before. Don't know what made me do it but I googled "what is my IP address?" and at the very top of all the responses was my IP address. I keyed this in to the URL space and guess what - up came my router home screen which I was able to explore, sign in using the sky default user id and password and look at everything I expected to see.

Now I am wondering whether I should be doing this or is it insecure.?