I assume you are crossing over from Portsmouth. This is my "local" ferry port and it is very busy at all times, even off season,and I am not too sure if the authorities would look favourably upon extended stays before embarking. You don't say for how long you wish to stay at the por, or where you are travelling from.If you are looking for an overnight stay there are CC Club sites at Winchester (Portsmouth 40 minutes) and Rookesbury Park, Fareham (Portsmouth 30 mins)and a commercial site at Southsea. If you are looking for an extended rest stop before embarking then there is a service station on the M27 (Rownhams)approx 30 mins from Portsmouth. Hope this helps. Get back to me if I can be of further help.