Taking Blade as an example 22.07 USD seems typical and fair, thats 14.7 UKP to save you looking it up. I got that price from DVDDynamic.
In would have recommended play247 but their R1 prices seem to have just made a jump so their price for Blade R1 is 17.99 UKP, for R2 14.99 UKP
Both include free(!) UK delivery which is normal apart from Amazon.com