I used to be very pro-tunnel. But you have to be aware they can invalidate your ticket on a whim (and if its a return ticket, that means you are force to pay nearly £200 to get home). Best avoided at all costs.
A longer ferry, say Plymouth-Caen, allows a bit of a relax, even a kip, after the 4-5hr trip from Leeds, and gets you a bit nearer. Best of all, it avoids Calais
I've taken my Omegas over there several times, and its going again in June.
Having suffered a failed crank sensor in France, and the car being delivered back to Blighty several days after I got home, I'd recommend all V6 owners take one
.
Don't treat the toll roads like German Autobahns. The local authorities take a dim view, and Brits are easy targets. Off the tolls, the limits are lower (normally 90k, motorways/tolls are 130k in dry, 110k in wet) but you get to see more.