Hi - I believe the 9 month old thread my have been mine so I though I would give you a summary of our trip. We travelled in F to Barbados BGI last July and I asked a similar question. Our experience was that the Gatwick lounge was quiet and comfortable with good selection of pastries, wines and the bacon roll was delicious. We had a long walk to the gate but it wasnt over the high bridge.
My warning is for arrivals in Barbados (it may have been that we were two females, first time in Barbados and looking lost). As F passengers we were one of the first to disembark and walk over to the terminal. We joined the queue for immigration but were directed (only us) to the VIP immigration desk - great we thought and we were quickly through immigration. I was carrying 200 cigarettes (a gift for a friend) which I had bought on the plane and were in a transparent carrier bag. We were then directed to a separate customs area where they told us that all tobacco imported had to be charged an import tax or they would confiscate it. My travelling friend (more experience traveller than myself was having none of this and argued that it wouldnt be sold on the flight if we couldnt import it - I'm not sure who was actually right but other passengers were going through another customs desk carrying cigarettes with no problem).
Also on the return journey although we were able to use the separate First Class lounge, as we had bought duty free items in Bridgetown (these are taken directly to the main airport terminal where you collect them once you have checked in) we had to use the main terminal. There is a separate desk for First class passengers but when we arrived the passengers checking in there were Economy (group of approximately 12) with Barbadian passports who were friendly with the Check In lady. They even called over their friends from another queue so that they were all checked in and seating together. There is a lounge upstairs for use by BA Club or First passengers but when you are called, you have to queue with the rest of the flight passengers. I went to the front of the queue and was told there was no separate queue for Club or First so we joined the end of a long queue. We may have been very unlucky but having flown in First before to Miami I can say that this experience was quite different even considering the strict US immigration procedures. In summary, if you buy duty free on the outbound flight, put it in your hand luggate and for the return flight use the separate FirstClass lounge facility. Have a lovely holiday - the island is beautiful - I would have loved to have gone there on Concorde but discovered BA Miles too late.