Connecting to Southampton Cruise Terminal, & Excess Baggage from Geneva
I would suggest BA into LHR and then the Rail Air connection to Reading [£22 return] and rail Reading - Southampton [£24 off peak return]. Costs are per person.
BA baggage allowance of 23K plus hand baggage allowance will come in at about 60K for you both. My wife and I have been on a number of cruises and would suggest that that should be enough for the average 2 week cruise around the UK.