You'd want to be down there before 7 to be sure to get a space in the actual station car park. it's fairly slim pickings after that. I usually use the harbour access road though.fairly OK over there til about 7:20 or so. Having said that they are doing some road works on that road right now and i think there are some parking restrictions in place. Better off cycling if you're getting a later train to be honest, if it'd ever stop bloody raining.