Having lived in a flat for the last few years I'm a little new to
gardening. The new place has a 20m long 2m high privet hedge that is
going to need it's first trim pretty soon. How often will I have to
think about doing this? I've no idea how long ago it was done.

There seem a vast variety of hedge trimmers around. I'm attracted to
cordless since the base of the hedge seems to get some use as a dog
toilet and until I have tutored local dog owners in the ways of
righteousness I'd almost certainly end up dragging an extension lead
through the crap.

So - recommended brand, blade length and power (assuming voltage varies
as it does for cordless drills). A cheap online supplier would also be
appreciated (or should i just go to B&Q or Argos?)

thanks

AJ