Did you use any particularly special controller? I presume one could use a
basic timeswitch/room thermostat combo (or zoned set thereof) doing the CH
rad pump (and zone valves), with a thermostat on the thermal store doing
the boiler control? And couple the primary circuit pump to the boiler
control**

No, my system is bog standard S-Plan-Plus off the boiler. Standard 2 channel
programmer, with both CH and HW to always on. 4 zones, 3 heating (to be
expanded to 5) and 1 for the heat bank. All heating zones have programmable
thermostats.

Had I run the radiators through the heatbank, I would have used a slightly
unusual control system, due to the radiator positioning requirements I have.
Basically, I would have a second plate exchanger pumped loop. The other side
of this exchanger would have been a sealed pressurised circuit, subdivided
using S-Plan-Plus zone valve, pump and controls to the radiator zones. This
gives the advantage of limited leakage, leakage detection, high mounted
radiators and pressure fill, which might as well be used downstairs and well
as in the loft conversion.

The gravity primary circuit would then only be used within the heat bank,
the DHW and CH plate exchanger loops and the boiler (although indirect would
also work, assuming a coil that matches the boiler's output).

Christian.