As you're obviously unfamiliar with ferry travel, I'd suggest taking either a day trip or a short break to Calais, to see if you enjoy it (That, of course, assumes that Dover is fairly easy for you to get to on public transport). As Dzug states (and the first link shows) it's easy to get into the town centre. Calais is often unjustly maligned by those Brits who are only happy if they can find big shopping centres, with pubs serving British beer and restaurants serving steak & chips. If your tastes are more civilized, you'll probably love Calais. It's quite an attractive town, with plenty of small, independent shops selling good wines and cheeses. There are also loads of good places to eat and drink. I highly recommend 'Au Calice' on the Boulevard Jacquard (which is one of the main streets).
If you're staying in France for a few days, Calais Ville train station is close to the centre of the town and you can get to plenty of interesting places fairly easily.