Its quite a bizzare thing to watch, but people will queue in a train so they can exit to doors nearest the exit. So even if you extend the platform to 12 coaches, as long as the exit is next to a certain coach, you will get people queuing to get off at one, or perhaps 2 doors. I've watched it happen at Billingshurt, Arundel, Burgess hill, Polegate etc etc. Having the exit in the middle helps quite a bit, having two exits from the platform speeds things up.
For up platforms its not such a problem. People heading into london will spread themselves along the platform. Shoreham by Sea is a good one. the down is 7, the up is 12. Coming from london the regs will head to coach 1 as that is where the exit is, with only the odd one or two getting off from coach 4 back. On the up, as its 12 they will spread nicely along the plaform during their wait for the train. So, no point in making the down any longer.
There are so many times at places like billingshurst on the down during rush hour, there is such a crush of people in coach one, you think, right thats it, everyone is off, then another body pops out of door 1, then another.
With Littlehaven as well, due to people queuing to get off the down platform you also have to be careful leaving the station as folks are so close to the edge of the platform. By all means extend the platform, but:
A Make it wider.
B Place a second exit half way up the platform.
With that you could cut dwel times by half and then clear the station, and thus the level crossing.
But thats only the thoughts of a lowly conductor.
