As the name suggests Mini Cruises from Southampton are shorter cruises; I have used the six night rule here for these cruises and will list all cruises of six nights or under below. Most cruise lines, indeed cruise ships tend to offer one or more mini cruises from Southampton; they tend to be used to try and attract people to the world of cruising.
How far can you get on a mini cruise from Southampton? Well an overnighter would be to the likes of Le Havre in France. Two and three nights might take you to Cork, Ireland or to Belgium or The Netherlands; add a couple of more nights and you cold find yourself on a round Britain cruise.