Could it be, just maybe, until they did their road show the other week, they did not have a UK distributor lined up (due to Ashes 13)? Unless that road trip was purely for preview by gaming media, etc, however coincided with the road show in India (and probably the same with South Africa) that was definitely aimed at distributors. You keep talking about 'Why has a retailer not put it up on Amazon'.. assuming there was someone who was promised the game on release who could put it up.. and that since they have been set up, they had been expressly informed not to announce release information until the marketing start date.
The only reason why Aus/NZ have had pre-orders available for months was due to the fact that Aus and NZ was the initial release countries back in July/November/Boxing Day.. but we kept getting pushed back to satisfy the rest of the world (don't hate me for thinking that way).