I went/going from Shoreham that is your best option as getting to Three bridges is more of a pain then going direct to East Croydon from Lancing. These are all covered by southern rail.
If you change at East Croydon then it's possible to get southern trains all the way to London Bridge, not too sure but think there is somewhere that you can buy the group tickets but can't remember where. Probably best to buy a week in advance to save the hastle
Made a club called Brighton on 360 if anyone wants to join, should have put FC on the end but wouldn't let me put the & Hove Albion as it was too long.