A suggested packing list:

Outdoor clothing which may get wet - 2 sets
Underwear - 4 sets
Toiletries and towel
Waterproof jacket
Hat and gloves
Footwear that can get wet
A PASSPORT if leaving UK waters is in the cruise plan

All bedding on board is provided, you do not need a sleeping bag

All your gear should be packed in a soft bag, there is no storage for suitcases on board

Please make sure you can reliably tie the following knots with your eyes closed BEFORE coming on the cruise:

Bowline

Clove hitch