Hi @TrainyUK,
I have a couple of troubleshooting steps for you to try find the root of this issue:
Attempt to access/download from the following three links, the attached file is a 787-10 livery. and just a redirect link to a website at the end: Root Link CDN Link Host Link
See if you can also access this site and download a test file of any size: Host Speed Test Link
If you can access NONE of the above links, then it is unfortunately a firewall or configuration issue on your network, computer or a rule set by your ISP.
Further troubleshooting steps you can take are testing the above links on a mobile/laptop device on the same network, if it works on the same network, this would indicate that the issue is to do with a network/firewall configuration on your computer only blocking our downloads server. If you'd like to take the time to troubleshoot further, you can try connecting to a cellular LTE/4G network and see if the above links work on it.
I look forward to hearing the results.