Both in-store and online. At £1.50 they are cheapest available. If you like them it's a good deal for 300g of delicious Mint Chocolate. According to Tesco the price is even better than half as it was 3.05 ;P Offer ends in 4 days.
Nestlé After Eight Mint Chocolate Half-Price (300g) £1.50 @ Tesco (Instore&Online)