In my experience these Findmypast subscription offers are not what they appear to be. I took advantage of their latest 10% off a Full subscription offer. When completing the application I was charged the full amount. On checking "My Account Details" I saw that what they were offering was the 10% discount when my subscription is automatically renewed in 6 months time. This discount(Loyalty Discount) is normal and not a special offer at all.
I have demanded a full refund under the distant selling regulations.