They claim 120L available at 20LPM at a 40C dT from the 40L primary store (78C) presumably as the boiler will be firing at 35kw output as well.
Any idea of the continuous flowrate at say 40C once the store has fallen to say 50C?, there will obviously be a dT between the PHE and the DHW temperature, is say 16.0/16.5LPM at 40C achievable at a mains/DHW dT of 30C.