Does anyone use online food shopping in Spain ? Which supermarket offers the best service ?

I have used Mercandona in the past. Less than 8 euros delivery if I remember correctly and on time. I used it just for heavy goods, nothing to compare it with sorry not much help.

Mercadona provide a good service from their store in Rojales. It may be better or worse where you live.

I use Mercadona they made my account in English so you can order in English if your Spanish is not so good.
8 euros delivery but very reliable and efficient.
Mas y Mas has started doing deliveries , but I think it depends on where you stay.

That's great info , thanks all .... !