How are you going to travel to work. If its by train then it depends where you live and if you are going to have to get the train into town before you head to brighton. Also what time will you start work because outside of rush hour would be a breeze.
I used to commute from Portsmouth to Cental London on the train - used to take me about two hours each way - including walking from the train station. I used to do that okay (I just used to kip on the train !!)