If you are in Havana between 21 and 24 November I'll meet you for a Mojito.
USD is far more useful than GBP but there are a fair few ATMs around these days, including as soon as you arrive at the airport. The ones in the terminal tend to have long queues but there are a couple more in the concourse across the road. I just withdraw CUC on arrival.
There are a few tips here, have a read: https://forum.tz-uk.com/showthread.p...ny-Tips-please!
And a bunch of photographs and other info here: https://forum.tz-uk.com/showthread.php?343212-Havana
Cheers, Matthew