Thanks for your thoughts.
Boiling kitchen tap has been given a big thumbs down by "the boss"
The kitchen sink is on an island, with the pipework having to run under the beam and insulated block floor, so not ideal and another reason I thought the recirculating system would be a good idea.
I'm planning on using a WBS with back boiler, gas system boiler and any excess solar PV, which is why I thought a thermal store was the way to go.