Seems like a pretty great deal to me for an amazing show! Nothing beats Frasier.
And you get £1 voucher back for Amazon Video. "Enjoy £1.00 credit to spend on movies or TV on Amazon Video when you purchase a DVD or Blu-ray offered by Amazon.co.uk. A maximum of 1 credit per customer applies. UK customers only. Offer ends at 23:59 GMT on Wednesday, November 30, 2016 '