I think the Ultimate Passes are only valid from 27th March so I would presume that they can only be collected from then? I don't think they are offering renewals with it being a brand new pass?
The buy now pay later option is explained on the benefits page of their website in the T&Cs section https://www.draytonmanor.co.uk/ultimate-pass/ultimate-pass-benefits
The buy now pay later option is explained on the benefits page of their website in the T&Cs section https://www.draytonmanor.co.uk/ultimate-pass/ultimate-pass-benefits