Rather worried about giving my financial details, as I'm not aiming to stay on FindMyPast and there's only a short free trial time (and I'm a bit forgetful).
I don't think you have to give any financial details to create an account to use this free offer on the 1939 Register only. You do NOT have to click on
(Start free trial) at the top right of the page which is for the whole site, and always available.
By the way, previous FindMyPast freebies have closed at
10am on the stated end day, not 1 minute to midnight as with other sites. This may have changed, but don't rely on having all day on 8th.