I used the Tesco Price Checker website and did a search for "patches". Tesco were offering Nicorette Patches (7 pack) for £8.50 (usual price around £12.50)
I printed off the page and took it into the store, after a short but polite debate with the customer service lady and a quick chat with the Duty Manager he agreed that they had to honour the price. Before I paid I told her to hang on and went and got another pack!
This was at Tesco Sidcup but no reason why, if the site is still advertising at £8.50, that all stores should sell for the reduced price. BE QUICK before they change it!