Post Editor Not Loading On Specific Wifi Network

This is an absolute random out of the blue issue that appeared on my site this morning.

The problem:

The post visual editor appears blank, no tiny mce, add media no longer works, add featured image opens a new tab, post scheduler not working and links such as Quick Edit no longer work.

The strange bit is that this is only happening to me and one other staff member, both of whom are with the same ISP but in different locations in the same city.

Staff on other ISPs can access all the post editor features

Staff in other locations can access all the post editor features

I can access the post editor features on a 3G network

I have the same version of the website hosted on a different shared hosting environment and have no issues

I have another website on the same vps as my current website (the one with the issues) and can access the post editor as normal

I have tried plugin/theme deactivation plus config.php suggestions and nothing worked but the fact that staff not on this ISP can access the site is what really baffles.

Has anyone had this issue? This literally became a problem sometime between midnight and 8am this morning