The only things you cannot use them for is deposits for spiders, and shipping cost. 

The voucher is a single use discount code that will be emailed to you after purchase.

To redeem the voucher simply add the single use code to the discount code section on check out and your order total will automatically deduct the voucher amount. 

You cannot split the voucher across several orders. 

For an extra fee you can have the voucher mailed to you along with a card and personalised handwritten message that you can leave in the comments box  at checkout.