We live in Lancashire, the best route from up North is Portsmouth to Le Havre, with LD lines, if your missus is going get the sleeper seats booked they're worth every penny I've done crossings from Dover too but its a hellish drive down.
October weather will start to be chilly at night, we had a couple of nights last week were the temperature dropped and there was ice on the ground sheet, daytime was scorching though, just take warm clothes / fleece and hats just in case it gets cold in the bivvy.