Re: Clearly I've missed something but
If the M27 is very busy try Lymington -> Yarmouth, drive to Cowes, over the floating bridge to East Cowes, drive to Fishbourne, ferry to Portsmouth. Shop, Return.
If the M27 is very busy try Lymington -> Yarmouth, drive to Cowes, over the floating bridge to East Cowes, drive to Fishbourne, ferry to Portsmouth. Shop, Return.