Hi Mark ... the charges have been in force at some airports since last summer. Usually, there is no drop-off charge, as drop-offs are relatively brief and do not involve cars sitting outside the terminal for a long period of time. Pick-ups are not allowed outside some airport terminals, drivers are instead re-directed to a designated pick-up point within one of the nearest car parks, where a pick-up fee is charged.
Glasgow, Manchester and Belfast Intl are some of the airports to have made changes so far. You can usually find details on individual airport websites, probably under the 'getting there' or 'to and from the airport' sections.
David