I'm not sure why but I've only had problems with Wiggle when I've paid for next day delivery. Most orders (including one today) are processed in a few hours so I expect some Haribo to be delivered to my office on Monday :-)
Sorry to hear of the problems.
I have never paid for next day delivery as more often then not it's delivered pretty quick anyway.
Same for me, I usually take the free postage option and it turns up quickly. I was just hoping to fit the new tyres to give them a spin tomorrow before the 100 so figured I'd pay the £3 to guarantee it.
What bothers me more is the absence of contact. In my work, I map out customer journeys & this strikes me of a company based on tight margins hence the lack of a contact number and their chat being available at limited times. When you consider I have spent £hundreds with them over time on what are often considered purchases, it is a bit frustrating. Tesco for example have a phone line so if your online shop is delivered and the £1 grapes are short dated, you can call and they refund immediately.