As has been answered, in UK NO, just military and special units of police carry.
For EU (European Union, the promised land of milk and honey that UK decided lo leave...) you, as said, have many different laws.
For as far as I know you (In Spain) CAN CCW while performing a CP role IF you have a contract approved by the homeland ministry and apply for the temporal license on advance OR get an exception when arriving to the country.
ALSO, in EU you have an "european gun license" that recognizes your (from other EU country) right to have and use weapons, provided you are following the requirements form your original license AND the weird ones that your host state may have on top of them.
Usually to be allowed to hire armed guarding you need to apply and defend your need for arms and of you are granted the exemption you will be allowed to hire a company or individual (registered CP) checked by homeland ministry who will have the license for CCW. Also, if this is a requirement for a place and not a personal protection, you usually are allowed (showing the importance of the items/location to protect) to hire companies with UNIFORMED armed guards just with open carry licenses, in Spain 38 caliber revolvers and 12 gauge shotguns (or for "county estates" any kind of long gun barreled in handgun calibers; but at least they can be self employed).