There are two options. You can take the EPS plinth insulation right down to the ground and then take the UdiPERL render down to the ground too. Or, you can use the UdiBASE plinth rail, fixed just above dpc level usually or at around 150mm above ground if no DPC is visible. It is important to remember that none of the Diffutherm wood fibre should be less than 300mm above ground level in either case.
The UdiBASE plinth slurry should be used behind the EPS plinth insulation to ensure full contact with the masonry behind, you may need to render this flat first if it's uneven. Once you have put the UdiFOUNDATION COAT render on, remember to apply a slurry of the UdiBASE plinth slurry over this and leave to dry for 24 hours before you apply your primer.