Anyone come up with design u-values needed to ensure the SAP target gets hit. The target needs to be hit by u-value improvements alone [no renewables]

I know we would all like to massively improve on the minimum compliance but in some cases the client will insist on the minimum standard required. Obviously the base case u-values need to be improved upon to hit the target , but by how much? Anyone come up with a rule of thumb yet?

The wall u-value is predetermined at 0.35W/m2K so I hope to hit the target by improvements to floors [ground bearing slab] and roof [trussed rafters]

Thanks in adavance, Mike