Rubber Safety Tanks

Age of rubber safety tanks is limited to five years by an FIA regulation (plus a possible two year extension after inspection by the manufacturer). Up until this year, it has been allowed to replace a rubber tank with an aluminium ditto, but in the latest Appendix K, this is no longer allowed. I wonder how the five year limit is applied in national UK races (and other countries as well). Is it strictly applied in, for example, Formula Atlantic, the Derek Bell Trophy, etc, etc where cars originally equipped with rubber tanks participate.