Please use this PayPal button if you have a PayPal account and enter the amount (don't use a £ sign).
If you don't have a PayPal account please use these buttons to pay by card.
Unfortunately it's not possible to enter an actual amount.
Click various amounts. Then on the next page you can up the quantity of each amount to make the total.
Then click the grey "Check Out" box under the orange PayPal.
The total amount in your shopping trolley is at the top right of the page.