Did you ask this over on another cruise web site too??!!
Brasil - EU nationals do not require a visa.
CAPE VERDE: Entry requirements for UK nationals: UK passport holders require a valid passport. A visa is required unless travelling in an organised tourist group and holding a 'Certificado Colectivo de Identidade et Viagem'. Individual travellers should obtain a visa prior to travel, unless there is no diplomatic representation of Cape Verde in their country, in which case a visa may be obtained at the airport on arrival.
So I would check with the cruise line to see if they have organised this tourist group visa.
And on that 'other' website you are not allowed to post links but I would seriously suggest that you go to
http://boards.cruisecritic.com/ and scroll down to the ports of call section to find useful info about your ports. Invaluable.