As above, link for Amazon but Tesco Entertainment also have this for £49.99 so depends who you prefer. Cheapest I've found at the moment but let me know if it's a better deal elsewhere.
8% Quidco available at Tesco (Thanks airdsuk) so bringing it down to under £47 there.
Not sure if available instore at Tesco.
Still, seems a great price for an excellent series!