Cairyran Ferry to Ireland

Hi, we are travelling on the Cairyran Ferry to Ireland From Sussex as we want to go to the Giants Causeway as part of an Irish trip but we are hoping to leave sussex 6pm to travel up as far as maybe Staff/Preston and find somewhere to put up either a Cl site which excepts late arrivial/early leaving or maybe a Motorway safe stop on or near the M6. To get the ferry next day early afternoon. Any help would be great. Or any tips on this route or Ireland touring.