Q: Would I want direct or indirect? Direct seems simpler - pump the boiler
primary through the bulk of the tank and the rads.

It has significant advantages and disadvantages. The main advantage is that
it allows the boiler to reheat the store in a very efficient manner, dumping
its full load into the cylinder, rather than relying on an indirect coil
that might not be able to transfer as much heat. This is particularly useful
if you are running radiators off the store. It also allows the boiler to use
a lower flow temperature (good for condensing) as there is no need to
provide a temperature differential that a heat exchanger would require. You
can run the boiler at 75C, rather than 82-85C.

The main disadvantage is that it doesn't allow sealed pressurised operation
of the boiler, a system which has a number of advantages, such as leak
detection and protection, pump over prevention, easier filling & flushing,
allowing radiators high up, etc.

So - from people that fitted thermal store cylinders: are they any good
and which one did you use? Any general theories/opinions also most welcome
:-)

I have a DPS Pandora heat bank (you refer to these as the "heatweb"). It is
an indirect type, as there are likely to be radiators as the highest point
in the system, so I wanted sealed pressurised operation. The rads are off
the boiler primary, not from the heat bank.

It is absolutely excellent and works entirely as described. It has been
fitted for over a year and I still haven't had to top it up (manual fill
version). I believe the Gledhill may be technically superior to the model I
have. In particular, it is my understanding that the Gledhill varies pump
speed to maintain heat bank stratification. However, I haven't in practice
found destratification to be a problem as the system never really runs out
of hot water.

The biggest test was filling a 750 litre birthing pool to 40C. It managed
this in just over 40 minutes, although the outlet temperature did drop to
about the required 40C by the time it had completed.

In conclusion, I would definitely fit this type of system again. Although my
parent's Megaflo also provides excellent performance, I prefer the easy
maintenance of the heat bank.

BTW, I'd avoid the traditional thermal store type devices. I would only
choose a model with a plate heat exchanger for DHW operation.

Christian.