It is often spoken of how budget is a concern for HBO when adequately transferring book to film. I have had an idea for you that may solve budgetary costs. One of the adaptations for a Terry Pratchett novel (It may well have been The Colour of Magic although I am uncertain) called an open casting call to fans to take part in filming as extras. A Song of Ice and Fire is one of the most popular fantasy series in the world, and has a global fan-base, particularly in Western Europe and is perhaps on par with Pratchett in terms of adoration by enthusiasts. With the UK and Ireland specifically in mind, perhaps costs could be cut by posting a similar invite to fans to volunteer to appear in Game of Thrones to enable you to spend money elsewhere on special effects, exotic locations or casting more well known actors? This would seem more economic than spending money on paid extras. But that's just my two cents.