Just back from town and noticed that Sainsbury's had halo 3 for £10 instore.
The ballymena store had 2 instock both with a £10 sticker on them.
Next cheapest seems to be £14.99 @ shopto
This is for the xbox 360
Advice - Ring up before you go to sainsburys and check so far ballymena is the only one this is confirmed for.