rockyfella:
How do you bank it?
You can only do it at the checkout - if you are not buying now, just add something to your basket (enough to get to the value that the voucher can be used for, in this case £50) choose a delivery time and go to the checkout.
At the checkout, in the top right is a section called "a) eCoupons & Clubcard vouchers", click on the "Use coupons & vouchers" button.
On the next page you can enter each code separately, and they will all remain 'banked' until you use them or their date runs out.