Found this on the Official Xbox Forums and it works. Games are; The Maw Toy Soldiers This offer ends on the 31st March 2013, so get redeeming if you want it.
Maybe they figured out people were using this without buying their chips. I managed to get both games this morning, luckily.
The games will work as trials unless you redeem a code or purchase the full version, the Toy Soldiers trial can be downloaded here: https://digiex.net/downloads/downlo.../3878-toy-soldiers-arcade-trial-download.html
I highly recommend The Maw, and once you're done with the main game there's still three other DLC game packs which only cost 100 MSP. It definitely adds life to the game. I'm really glad I got this for free because it was how I got to discover this game, otherwise I'd never have noticed it existed or it was this good! Same thing happened with The Walking Dead, downloaded the first episode free of charge and then bought the rest. They should make more offers like these.