The Visa Waiver Program is primarily designed for short tourist visits. The B-2 is the standard visa for visitors who travel frequently to the US for business or pleasure. It is a multiple entry visa that is valid for ten (10) years and allows a visitor to stay for up to 6 months at a time.
The Visa Waiver Program allows visa-less entry for up to ninety (90) days for nationals from certain countries--UK included. The regulations do not specifiy how often the VWP can be used, but someone who uses it 3-4 times a year will probably come under scrutiny eventually. Now that there is pre-clearance application (ESTA) that may not be as much of a consideration. But VWP is not designed for the frequent traveller to the US. If it hasn't been a problem for you up to this point, it probably won't be in the future. Overuse could raise questions though.
The application for the B-2 is usually submitted to the US Embassy or designated consulates in the applicant's home country. It involves a face to face interview. The application though can be submitted at any Embassy so you could apply at the US Interests Section in Havana.
