Take the biggest case you have within the hand-baggage dimensions limit even if you don't fill it, you'll need at least one change of clothes for the return cos hold luggage (remember to pack shower gel, sunblock etc if in containers bigger than 100ml) is collected the evening before you get back to Barbados.
Sorry, but Thos Cook flights are pretty awful - my return flight was in the most cramped aircraft seat I've ever experienced, even on short-haul, both for width & legroom. Go premium if you can. But not all their aircraft have the same layout so mebbe you'll be lucky. And don't let a cramped flight worry you too much - the holiday was fantastic. Flight time out about 9 hours, back about 8 hrs. Chris.
Flew from Gatwick to Barbados on 13th December. Flight left on time and had no complaints re. comfort. We had a row of just 2 seats near the back of the craft. Food was OK, but distinct lack of films available to view unless you were in Premier class. Saw several people with cases on wheels, which they took on as hand luggage.
A small wheeled case should not be a problem and can be very useful given that your main cases have to be packed and outside your cabin door the night before you arrive back in Barbados and disembark. At least you will have something to pack a few clothes into (but don't forget liquids are still restricted). Check your tickets and the OV website for baggage allowances and restrictions.
Thanks for the Question Williams, we were a little worried ourselves. We to are travelling out to meet Ventura from Gatwitck to Barbados. Hope you enjoy or have enjoyed your trip.
Chris and Dave.