Hello,
I recently placed an order from my mobile, logged in to scan.co.uk, item in the basket showed the correct £0.00 charge for delivery. Went to pay with PayPal but had an issue getting it to take the selected payment method (the PayPal window with payment options would open and then close when selecting the chosen method, but the checkout page did not reflect the change) I tried several times to change the payment method to no avail - so just paid with the default payment method. When it completed checkout I noticed the delivery charge had been added back on!
I opened a web note and spoke with someone regarding this issue, he stated that I'd completed checkout as guest. I thought that was strange as I definitley had logged in, but figured it could have been something to do with the issue I was having with PayPal. Now having seen many other users having the same issue I decided to open this post in the hopes this may be resolved.
Edit: after looking at some more recent posts and the lack of anything coming back from scan it seems like this was a waste of time too.