Earlier I had a call following up my email to BBC Watchdog (I cc'd it to Tesco Direct) to apologise for all inconvenience caused and to offer a further refund of £15. However, another emailer just had a reply stating the Terms & Conditions and apologising further. I guess the emailer either worded their email quite strongly, or didn't involve Watchdog. Also, another user('s wife) is having talks with Trading Standards.
We all knew it was an honest mistake - EF-S 17-85mm and EF-S 17-55mm are VERY alike - but Tesco haven't handled the entire thing very well. Included in that bad-handling was leaving the page up for more than 24-hours after the error was noticed. All other points-of-sale were sorted; but they just couldn't remove a web page.
This might have started out as a bargin-grab, but it then turned towards making Tesco's malpractice clear. We must do all we can to fight against what might be a dupe for greater web-traffic and product orders.
This is the first time I've ever done anything like this. All the time I felt like I was channeling my brother, who is pure 'this'! It was fun, and I hope it works out as well for others who are waiting on a refund as it has for myself

Regards,
Henry