If I begin the purim seudah in house A can I go to house B to visit and then back to house A continue to eat and/or bench?
Yes, this can be done, but you should have explicit intent upon beginning the meal that you will be going to visit B.
Sources: See Rema, Orach Chaim 178:2, and Mishnah Berurah 178:33, 40. If one forgot to have intent, it would remain permitted to go if one leaves behind somebody who is a part of the meal. If nobody is staying behind, and one did not have intent at the time of one it would still be permitted to leave for a mitzvah, but in the case of going to visit a friend one would lechatchilah have to bench before leaving.