Staying strictly on topic, is the London<->Calais SDR a CIV ticket? CIV wasn't printed on mine. If they are CIV, would someone have to put me up at Dover if the last sensible Calais>Dover boat were delayed, and I consequently missed the last Dover>London?
Given there's no element of continental rail travel involved, I suspect it probably isn't covered under CIV. Willing to be proven wrong though.