Randomly searching the store and noticed series 7 was only £4.99.
For 16 episodes (I listen to my phone at work) this is brilliant.
All other seasons are £18.49 with the more recent ones even more so.
Great value in my opinion.
Update: Just noticed its now the same price on Amazon Video too (for anyone who has saved up their Super Saver £1 discounts). Again, its only on Season 7... which is weird.