The Housing Trust is taking away the district heating system which provides my property with central heating & hot water with individual gas boilers. They have quoted a (silly) price for installing a complete new system including new rads. The existing rads are fine & do not need replacing. I want to choose my own boiler and was considering the Ravenheat HE System Condensing Boiler. apparently you don't need a hot water expansion tank with this. I have a lagged hot water tank but no immersion heater. Is this the correct boiler for my system?