as it just so happens someone on another forum posted this link yesterday. good timing or what!
http://www.cheap4ferries.com/default.aspxAlso look at teletext for great last minute deals. My Dad used to spend ages looking through for bargain fares.
Another option is to convert your Tesco clubcard vouchers into online points and if you have enough you can get a free ferry or discounted one. A mate has travelled to France twice now with a caravan and not paid for thier trip on the Ferry by using Tesco points.