Is this good or bad practice. Should I install isolation valves on the ch
flow and return and the dhw in/out, about 6 inches under the boiler
connections (obviously making allowances for the filling loop and it's
connectors, etc).

Haven't really thought through the benefits of this, or the cons
(un-nessecary restrisctions right at the start of the runs, maybe), but just
thought I'd check with the group.

I'm guessing that there's no real need?

Jon