Leaving aside the odd few moments in the year when the mains water supply is turned off in the street due to roadworks on maintenance, if you were to totally replumb your home would you put in a condensing boiler and remove the water tank in the loft so that everything in the house is on mains supply?
Surely the advantages out weigh the risks of potential leaks and flooding when freezing over in the winter?
Who still would have a tank and why?
Given the higher water pressure for showers etc I don't think there's much debate. Certainly with an unvented cylinder there's more 'knobs,bells & whistles', therefore there's a high maintainace cost, but I think that outweighs the disadvantages of low pressure systems & the potential problems of burst pipes & flooding with a tank/tanks in your attic.
Modern combi boilers are infinitely better than they were when they first appeared in the early 80s. Granted even a 35KW combi will only supply one outlet at any given time, the performance of these units are more than adaquit for most small homes, where hot water demand is small.
Most homes have dishwashers & washing machines that heat their own water, most people will have a shower at 34-38*C & many homes have electric showers that also generate their own hot water. So our hot water requirements have vastly reduced in the last 30-40 years, so is there a requirement for heating & storing hot water?? For most homes I'd say no.
Vented hot water systems & tanks in lofts are a product of the Victorian era. We have moved on in our 21 centurary.