This is the DVD version I presume?
I just had a look on Amazon (UK). Seems they have a bluray version for 17.99 pounds. That's doable. I saw it in a store here for 70 or 80 euros I think.
Serenity bluray 7.99 pounds.
Serenity DVD 3.18 pounds.
Firefly DVD 12.20 pounds.