Is it possible to install and run the above without it being connected to
a
boiler and just use the immersion,due to the cost I would like to add the
system boiler and radiators at a later date.

Entirely possible. It did exactly this with my heat bank. The boiler was
installed a month or two after the cylinder and it couldn't run off the old
boiler as the connections were above the level of the F&E tank. Are you
installing the thing yourself? If so, ensure that you are either aware of
all the safety devices (separate safety zone valve, manual reset
thermostats, pressure relief etc.) or install a heat bank instead.

Christian.