Pay over three months is an option offered by Paypal subject to your online application being accepted by them. Once accepted, Paypal allows you to pay over three month's interest-free.
You can apply for 'Pay in 3' when you check out - please see notes in the diagram below, in particular the section indicated by the blue arrow. The maximum limit imposed by Paypal on the "Pay in 3" is £2000.00.
This will be an agreement between you and Paypal and not Creative Printers of London. Failure to make payments on time will result in your future credit rating being affected and Paypal will charge interest on late payments. Please refer to their agreement for full facts and the amount of interest they are likely to charge on late payments.