Before you start your download, create a copy of your "company of heroes 2" folder in steam/steamapps/common/(game folders). Rename the copy folder "company of heroes 2 - copy" to "Company of heroes 2 - Press" and it will speed up your download by only fetching the british files needed for the download! Hope this helps speed things up!!!
For players who have lots of DLC content (like ardennes assault) steam may reject their installations and start from scratch. To prevent this, instead of the above instructions, you can make a "
company of heroes 2 - Press" file in steamapps/common/ and put a copy of your "company of heroes 2/CoH2" folder which has Archives,Locale,Movies inside of it. This won't let you copy the whole game, but will give you a significant boost.
source: reddit coh2
https://www.reddit.com/r/CompanyOfHeroes/comments/3j4ai0/copy_files_from_coh2_to_british_trial_to_dl_faster/