I came back Bs As-Tilbury on Grimaldi last June/July. It took 24 days including about six moored outside ports waiting for a berth (missed the Ripley HU meeting as a result of the delay; grrrrrrrrrrr!)
It was incredibly boring as I was the sole passenger once the two Germans in the next cabin had been arrested for the 19kg of cocaine concealed in their Unimog!
Great food, comfy cabin, wonderful to jump on the bike in the hold on return and just ride out of the port (the bike isn't on the manifest, it's luggage) and saw some fantastic marine life but, I think I'd only do it again if I had a partner with me.
Good firm to deal with too.