Ask Me: Former Strategy Consulting Recruiter
Happy to answer any consulting-related questions. I'm currently being sponsored by Deloitte S&O for my MBA. In consulting I focused on M&A in Europe and the US. I also led campus recruiting at two undergrad institutions.
Start networking now with the goal of being hired in summer / early fall. Most firms prefer to get ahead of their fall campus recruiting schedule, and would appreciate the opportunity to interview you early. In regards to timing, your one year full-time in banking is definitely sufficient (i.e. the consulting firms won't hold your not completing the full program against you). The experience will also outweigh your GPA, so don't worry about that metric. Top priority should be meeting peers and leaders at the firms you're interested in. Leverage your personal network and don't be afraid to make some cold calls. As long as you've got a strong story for why the switch from banking to consulting, I think you'll be happy with the level of interest you receive.