Your CPC qualifications are yours for life.
You can lose your ‘Good Repute’ if you get into trouble with the Traffic Commissioner if you were the nominated Transport Manager/CPC Holder for the errant company concerned. 
This will make it more difficult,but not impossible(depending on how serious the offences were) to become a nominated Transport Manager in the future.But even the Traffic Commissioners (who are more powerful than God, bless 'em) cannot take those hard earned certificates away from you! 
I too, hold both National and International, (passed 1984) 