Charr Gate quest

The quest where you go through the gate and help the prince once you do this can you get back to the start area from there?

If you haven't gone to the Acadamy, you're still in the starting area. Going through the gate lets you into another part of the starting area. You can travel back to Ascalon City, or Ashford Abbey, etc. from there.

Yea i am in the starting area and have finished all the quests now, except Char Gates. Once I do this I go to some other land which I did before, but can you come back to the starting area or once you leave thats it unless you make a new char?

Only quest that prevents you from continuing in Pre-searing is:
http://gw.gamewikis.org/wiki/The_Path_to_Glory

Ah yea ok, its that one, so how else do you leave the start area then to head on to the other lands if you have finished all your quests there?

thats the only way

Ok, I may be wrong but I believe the OP is talking about the Northlands in pre. The Charr at the gate is the quest where you go with Rurik to kill those few charr standing by the gate to the northlands.

Go to Wiki for a complete quests list.