BMI Diamond Club has already been closed to non-UK members since December 31, 2012, after British Airways acquired the airline (and took over the LHR slots).
Members in the UK that have had the BMI Diamond Club affiliated credit card had been able to earn Avios at a favorable rate (compared to BA products) and also were eligible for a 10% discount off of BA flights.
You can access Diamond Club’s website here.
You can only earn Avios on the Diamond Club credit card until September 30, 2016. You must combine your Diamond Club Avios to British Airways Executive Club ones by November 30, 2016. That is also the last date to book BA flights at 10% discount.
Here’s what BA posted on the site:
We are sorry to inform you that the Diamond Club will be closing on 30 November 2016.
Please be assured that up until this date, you can still use your 10% discount on British Airways flights.
If you have a Diamond Club Credit Card issued by MBNA Limited, you will no longer be able to collect Destinations miles from 30 September 2016, however you will be able to convert them in to Avios using the Combine My Avios tool when you log in to your Executive Club account [hyperlink to www.ba.com/executiveclub]. You will need to do this by 30 November 2016, otherwise your miles will not be transferred and will expire.
Combine My Avios https://www.britishairways.com/travel/btt/execclub/_gf/en_gb
If you are not already a British Airways Executive Club member, please join at www.ba.com/join
BMI’s Diamond Club was the richest frequent flier program that I have ever come across, although it was quite a PITA trying to book awards with their call center in India. You needed to be persistent and know the award availability before you called in.
Not sure if any other program would allow flying from Havana to Abidjan with a stopover in Sao Paulo? This was before COPA joined the alliance and only way out was to use Air Canada.