Upgrade water heater cylinder

Hi. You could use a main fed thermal store, they aren't cheap but work well. You would need a site survey for suitability.

unvented cylinder gives you mains pressure hot water,get your main tested for pressure and volume first to check it is sufficient for cylinder,then you can do away with tank in loft,all cold taps off main,you will then not need a pump .

You can replace the water cylinder with a unvented either direct meaning not heated by a gas boiler,Or indirect so it can be heated by your gas boiler both will have electric immersion heaters,Who ever does the job make sure they have completed & passed there unvented course to comply with the G3 building regulations.

you maybe need to replace pump, because if u connect from hot water cylinder, outlet in to the pump should pump hot water to all hot water, tap,and shower. if the pump do not running , the pump is gone

AN unvented cylinder has special requirements, that will need a site visit and an extra qualification G3 ( besides plumber or gas safe). It's not always possible- you need GOOD mains pressure and a way to take away the safety discharge, safely. The length of time to install will depend on the installation site, and the ancillary works, like access to the feed tank, changing toilet fill valve orifices, plus a check to confirm taps are suitable for high pressure. You may also want an additional electrical backup supply- which may require an electrician. If you have one installer that does electrics and unvented cylinders and access is easy then it would be 1-3 days. The unvented cylinder will need quite a large space for additional equipment, ( expansion vessels and zone valves) depending on the make, plus access for regular servicing, there are safety devices that require checks, which means the cylinder needs annual servicing.