Avoid Lands End unless you like the overprice, fake-Disney version of the place (which is all it is now).
For Padstow and St Ives be aware you can't take the car into the town (you wouldn't want to, anyway, believe me!), and have to park at the top ofthe town and walk down into it to sea level.
From Padstow, there's a nice ferry across to Rock.
By and large, south/Channel coast is for sailing, with lots of deep inlets of water (rias), and the north/Atlantic coast is rugged and wild for surfing and big beaches.