How to create an Ecommerce Loyalty scheme for customers? How can I create a 'loyalty scheme' where customers are awarded with 5 pence for every £ spent, to be used on furture purchases. The rewards will be saved up until the user decides to redeem them against an order. 

I have looked for a few solutions but cannot seem to find a way to make this work.

Any suggestions?
This may be too much overhead for your system of point usage, but check out the Commerce Userpoints module.  It integrates Commerce with the Userpoints module, which should handle most of what you're after.