I'm sorry I sounded so angry earlier on, I was in a bad mood and the BBC stopping me from playing a game I'd been looking forward to didn't help! I feel better now.
This website seems to be worth a shot
despite its dodgy spam-sounding address. Just go there, scroll down the page a bit to find the second Search box, input the Doctor Who website address - http://www.bbc.co.uk/doctorwho/
- and once there find the page for the Adventure Games. The page acts as a simple proxy, so you should be able to access the download page to download the game - albeit perhaps quite slowly. Mine's downloading now.