Part L2 (2021) requires an allowance to be made for non-repeating thermal bridging. In the VE implementation this is handled via a coefficient expressing this component of heat loss as a multiple of element area. This can be thought of as an addition to element U-value (10% for the notional building 25% for the actual building).
In the notional building, thermal bridging coefficients are set to standard values laid down in the NCM Modelling Guide.
