I get in the first carriage, allowing quick exit , through barriers, down to Jubilee Line, and usually straight onto first tube ,and its only three stops to CW. Admittedly if the train arrives at 18 minutes past it's unlikely, but the 'real' arrival time is 12 minutes past, altered decently to...
I commute from Durrington to Canary Wharf most days.
It's generally fine. I catch the 6:46 from Durrington, which is scheduled to arrive at LB at 8:18. I'm at my desk around 8:30.
Catching the train at Worthing you should always get a seat, which is more that can be said from Hove for...