soon to buy a 6 bedroom house, 3 showers, 2 kitchens. i need advice on a "rolls royce" central heating system. i've heard i should fit a megaflow system with a possible 250lt tank up in the loft extension. is this capacity enough? we would also like a water softner (Harvey Water Softner). contacted wocesterbosch and was advised that their heat exchangers in their new boiler range have an aluminium heat exchanger and is guaranteed for 10 years. but if i installed a water softner then the guarantee would be immediately void as the saline content of the salt would corrode the aluminium heat excahanger!.... can anyone recommend another rolls royce boiler and answer the other questions above.... pls not vaillant or baxi, have had bad experince on both of them. also is 250 lt tank enough as the next size is 300lt !!!!!!! oh also the "whole" house will have polyplumb underfloor heating system.