Please check your boiler model as I don't think Worcester make a 24CDi model. You refer to luke warm water which I would take as being the DHW. You are looking at various possibilities here like what flow rate do you have at the taps, what gas pressure at the burner when the boiler is running, what is the supply pressure at the boiler inlet. This before you look at the electrical control aspects, plate heat unit etc. Would suggest an engineer a look at this.