The latest version at time of writing is V 5.6.a [1] which is available as a download from the EPBD NCM website.
[2] It has recently underwent additional programming to allow it to be used for producing EPCs for Non-Domestic Buildings.
Several commercial software tools exist, offering a more 'user-friendly' front-end to the SBEM calculation engine than iSBEM.
The SBEM calculation engine has some limitations and is explicitly distributed as a 'Not a Design Tool'.
For more complex buildings, accredited Dynamic Simulation Modelling tools should be used for Part L compliance and EPCs.