Most cruise ships [no boats] reposition twice a year - they generally head west Oct/Nov so they can be in the Caribbean during the winter, and then head back to Europe around April/May for the summer season. You could try Cunard, I think this is the only line that regularly crosses the 'pond.
Royal Caribbean - Ovation of the Seas - 08 Mar 18 - 33nts
UK : Sydney : Milford Sound : Doubtful Sound : Dusky Sound : Dunedin : Wellington : Napier : Picton : Sydney : Brisbane : Darwin : Kuala Lumpur : Singapore : UK
Now from £3099pp
View More Amazing Tailor Made Deals!
Click here to see offer
P&O Cruises - Oceana - 20 Nov 17 - 9nts
Southampton : La Coruna (Spain) : Seville (Cadiz) : Gibraltar : Lisbon : Southapton
Now from £599pp
View All 2017 P&O Cruises >>
MSC Cruises - MSC Preziosa - 27 Sep 17 - 7nts
Southampton : Bruges : Amsterdam : Hamburg : Paris (Le Havre) : Southampton
Now from £649pp Was £999pp
Click Here To View More MSC Cruises From Southampton >>