Cheapest I can find this great game for today (although it was cheaper about 6 months ago). $5.99 which equates to £3.51 at today's exchange rate.
Legend of Grimrock is a dungeon crawling role playing game with an oldschool heart mated with modern execution. A group of prisoners are sentenced to certain death by exile to the secluded Mount Grimrock for vile crimes they may or may not have committed. Unbeknownst to the captives, the mountain is riddled with ancient tunnels, dungeons and tombs built by crumbled civilizations of days long past. If they ever wish to see daylight again and reclaim their freedom, the ragtag group of prisoners must form a team and descend through the mountain, level by level.
The game brings back an oldschool challenge with highly tactical real-time combat and grid-based movement, devious hidden switches and secrets as well as deadly traps and horrible monsters. Legend of Grimrock puts an emphasis on puzzles and exploration, and the wits and perception of the player are more important tools than even the sharpest of swords would be. And if you are a hardened dungeon crawling veteran and you crave an extra challenge, you can arm yourself with a stack of grid paper and turn on the Oldschool Mode, which disables the luxury of the automap! Are you ready for some classic dungeon-crawling first person perspective party-based RPG action? Are you ready to venture forth and unravel the mysteries of Mount Grimrock?