Do thermal stores really work?

Using a large DHW plate heat exchanger lopwer store temperatures can be used. They will revert to the boilers output when it is switched in and the store is exhausted. It will never run out of hot water, it will just slow up. As DHW is being drawn off, the energies of the boiler and the thermal store combine, so asmaller cylinder can be used.

Even if a stores setpoint temp of 80C the boiler condenses 80% of re-heat time. Run it at a lower setpoint temp and condensing is 90% of re-heat time.

They are thermal stores not heat banks (more efficient plate heat exchangers). A boiler with a delta T of 25C can easily condense.

With a setpoint of 80C, 80% of re-heat will be condensing. From cold: store temp 20C. he boiler raises the temp say 25C, that is a flow into the store of 45C, as the return water get hotter the flow get hotter. Approx 80% of reheat is below de-point.

Use two cylinder stats and a latching relay to prevent boiler cycling.

Fresh water not inside a thermals store - it is PRIMARY water, not secondary (fresh). Water softeners are required for "any" water system in hard water areas.

Yep.

Pressurised heat banks (using an external plate heat exchanger) are not in G3 - can be DIYed and no annual service charge.

New to me. Come again?

Unfortunately you are virtually 100% wrong.

as told by DPS techie...

A DIYer can fit a stainless thermal store. Making holes in it and putting an Essex flange is not wise.

Get a new stat and replace. A 15 minute job.