OK, so...
1) I copied Tequila to another PC, ran it and installed CoH there no problems.
2) I copied the newly downloaded CoH folder from that PC to my external drive
3) Deleted all CoH folders on the PC with the issue
4) Copied the CoH folder from external drive to PC with problem
5) Ran tequila from the newly copied folder
It works....
So it seems that although both PC's use the same router one can download it and the other cannot... very strange.
Either that or something changed between it failing on PC1 and working on PC2
No idea.. but at least it's working now, just hope I don't have to do this every patch!