[en] Codes developed in the UK for LWR reactor physics calculations are described and examples are given of their use. The codes cover both static and kinetic situations and can be used for fuel management and transient calculations in one, two or three dimensions. The first example describes validation of the static calculations by comparison with many cycles of PWR operation. The second one is a treatment of a difficult problem of double heterogeneity caused by discrete gadolinia particles in poison pins. The final section discusses static shutdown and rod ejection accident calculations to assess the adequacy of the control system in a PWR with the introduction of plutonium recycle. (author)