Yes. The first step of the 'checkout' process allows you to type in any special instructions. In the 'Regular instructions' box you can type in any standing or long-term instructions, such as 'always call at the back door'. These instructions will be saved. 

In the 'Special instructions for this order' box you can give us any instructions specific to the order, such as 'green bananas please' or 'call 01111 232425 if you need to contact me about this delivery'.