The Worcester-Bosch Greenstar will incorporate a 3-ways inside the case for
you; customer option. Neat and easy, and takes no space.

According to my manual, the internal diverter valve option would be very
good for most systems, as it appears to allow different temperatures to be
set for the hot water and heating sides of the valve. Unfortunately, the
maximum allowed is 75C on hot water, so is no good for a heat bank. Heating
side is normally limited to 75C, but can be boosted to 85C by flipping a
plastic insert.

Christian.