Hi lou 25 - ok, different Q.
UK citizens need the visa - get one from :
Ministerio de Turismo, Havana: +53 (0)7 334 323 or www.cubatravel.cu
or
Cuban Interest Section, Swiss Embassy, Washington DC, United States: +1 202 797 8518
or
Embassy of the Republic of Cuba, London, United Kingdom: +44 (0)20 7240 2488
You may need proof of booked accommodation or onward travel arrangements or proof of cost of living funds (of about $50 a day whilst in Cuba) if you are travelling outwith a normal tourist package which provides the terms anyway as it is a pre-booked affair. Check with the Embassy.
And the forum link offes the 'Sailing in Cuba' book title which looks useful to have available as the facilities may be quite basic, so be prepared.
Hope the is useful and have a peachy time . . .