There were some frustrated fans at Brighton station after the match too. We were herded (8 carriages of fans) through the 1 barrier open and then those of us who needed the London bound trains were herded back through another barrier, directly into the path of people from the London & West Coastway platforms trying to get to the only open barrier. Great fun ensued as a result.
Oh and as already pointed out, I only saw BTP not Sussex police there.