Not noticeably uphill or not noticeably quicker?
Trip 50 minutes in to Falmer on Saturday (quickest ever). Out to Shoreham is 90 minutes on a Saturday, longer in the evening.
Cycling say 14 mph allowing for traffic and it might be quicker to get home.
I was thinking of cycling from Shoreham because it would be quicker. London Road to Falmer is uphill though.
Train fare from Shoreham is £4.60 and back. Tickets checked at Brighton.