Na the re-download didn't work as the same problem persisted,
but all good now.
Pestered my boyfriend into helping as forcing verify, firewall removal, re-downloading and installing windows.net run didn't work
what we did was this:
computer/programmefiles(x86)/steam/steamapps/common/blacklightretribution/blacklightretribution/live/binaries/win32/BLR.exe
I then ran BLR and it highlighted missing files which turned out to be D3DCOMPLIER_43.dll
This file is found in this programme DirectX End-User Runtime Web Installer, so all I had to do was download that and install it.
After that everything was fine, ran BLR.exe again and the programme launched.
Thanks for the suggestions guys and hope this will helps if someone else gets into the same situation