Hi STEM,
Thanks for your quick reply! I'm a newby here and I'm impressed.
I have attached a picture of:
1. My NEST Heat link without the HW control (N used, L used, 1 empty, 2 linked to L, 3 used)
2. My HONEYWELL that just controls my HW: 2 water tanks in the loft, 2 hot water cylinders with...