Petition Shops should have to sell items to you at the advertised price. ie an advert should be an offer not an invitation to treat.

When you see an item in a shop window with a price tag on it saying £5.50, you might think that £5.50 is the price you must pay for that item.

But legally the shop is saying, "Make me an offer then I will decide whether to accept or not. Oh, how about you offer me £5.50 for it, I might accept that."

So, if you're in a shop and you see a bag with a label
"small bag £5.50" and you take it to the counter and the man behind the counter says "That will be £7.99 please," as the law is you would have to pay £7.99 or go home empty-handed, but I believe the price on the tag should be a legal offer so the shop has to sell the item to you at the advertised price.

Short legal explanation:
I want the display of an item with a price to be an offer to sell and not an invitation to treat.