done a bit of digging re this subject and it goes like this
Dover Calais if your rib is coded yes not a problem provided it meets with your insurers agreement
Portsmouth to Cherbourg no, too far
so boils down to coding , navigational waters , and insurer being ok with it, they may ask you to pay a one off premium to cover that particular event, again that could be down to qualifications experience, it depends on the individual insurer and how they assess the risk and what type of event it is .am talking about the commercial aspect not pleasure side
regards Tim
www.griffmarineservices.co.uk