yep, f***ed too.
i was at Lewes and they are cancelling all Eastbourne-Ore trains, which is a bit odd as you wonder where they are all hiding (trains from Eastbourne were running through and to Haywards Heath). there was also a emergency special running Brighton-Eastbourne-Hastings-London...
via "mid sussex route" which i dont know myself (horsham - littlehampton?) or via St Leonards Warrior Sq. quite possible to get down to Falmer, but the return will be a mare.
or car. imagine taxis from Three Bridges will be doing good business.