Depending what you want to do in Guernsey I have some info. You'll tender into St. Peters Port. This looks to be a cute little town to walk around in. There is an old fort as well as a wonderful old church. We're only there until 2pm and is our first stop after leaving London. We try to take it a little easy the first day as we're still trying to adjust to losing 8 hours sleep on the way over. Hope is helps.