You can always go into SC it's just a matter of binding the keys in the Option setup menu... you can bind one for direct jump to another system and you can bind one for just SC and if I remember correctly there is also one whitch switch between normal flight to Hyperspacejump via SC first...
You don't need to be lock at a target to enter SC only hyperspacejumps require a target locked to engage....
I personatly use spacebar to activate SC and if locked on a target system and then pressed again it initiate a jump...