Nikon P510 vs Canon eos 400d

[grimidol]

Hi i struggle with the auto focus on the P510 and want to try another camera.
With the P510 in manual focus you have to get the sizing in the frame right then pick manual focus ( it then in larges the area you are looking and so you can focus then when u are done goes back to the normal view and you can take the picture ... When trying to take pictures in the woods of animals this is not possible the bird has gone by the time you do this. In auto even with it on the center focus setting it will some time pick some thing outside that and then the bird is out of focus even when the bird is bid in the view finder.
With a full DSLR i am guessing they are more like my old Pentax ME super where you have a live manual focus you just slide up and down on the lens and when taking the picture the view finder stays live and not go black so you cannt see the image you are following ( the P510 on continuous shot goes black so you struggle to follow the bird if they fly off).
cheers not sure this is right part of forum but seeing as it is more about cameras and what they can do i though it would be here ?
Any advice on another camera second hand around the £100 to £200 mark as i don't have allot of money to play with.