241 vouchers mean that you get a free ticket when you buy a full price ticket. If you buy a standard full price adult ticket, you will receive either a child or adult ticket for free. If you buy a standard full price child ticket, you will receive a child ticket free.
A standard adult ticket is currently £50, and a child ticket is £46.
Unless otherwise stated on your voucher, this can only be redeemed at the entrance gate on the day of your visit, and is not valid with any other offer, on premium tickets or on free tickets. The expiry date will be listed on your voucher – after this date has passed, you will no longer be able to use this voucher.
We hope this answers your question.