Yes as just subject says you get two hours when you pay £14.00. Simply follow as below;
1) Pay £14.00 at B&Q store (where there is Hertz on demand service) and collect the Connect by Hertz pack.
2) Find the Offers and Discount leaflet in the pack and find the Promotion code (Mine it was 1191 - I assume this would be same) which says "Join the club for free and earn £15 free driving Credit".
3) Follow the link and create a profile in Heartzondemand website and insert your promotion code in the second page (if I am not mistaken) when you create your profile.
4) Then call their customer services team on 0207 365 4199 and book the time slot (2 hours).
I have booked mine today just for £14.00 and got two hours. Enjoy your two hours for price of one.