immersion heater tank & water tank installation

Yes its reliable. It would work if you could put the storage tank high enough. Materials could depend on where your buying it from, most plumbers work on a day rate too on big jobs, you looked into an unvented cylinder? If you have enough pressure on your incoming main I'd say that would be better fit. If your looking for a cheaper option you could get one of these.....https://www.plumbnation.co.uk/site/telford-direct-combination-cylinders/?gclid=Cj0KCQjwpLfzBRCRARIsAHuj6qWYETpIk7msbwM-oFtPzyi5Vd96kaj1YTVpnsPUK5F0kkPUM_bbx-UaAjiCEALw_wcB

Would all depend on number of hot taps to be delivered to, number of occupants in the home, is electrical in place in the cylinders supposed location?

Yes it can work quite well if you have a loft space & can get the storage tank high enough but chances are you may still want to pump showers, either separate pump or an all in 1 unit but you will need a minimum of a 70/50 storage tank. If water pressure is sufficient an unvented cylinder is perhaps your best option. Hope this helps.

The answer is good but I would also include the base support for the tank being either 18mm marine ply or wood