Argos are doing the dual guitar party pack for £36 at the moment. It's a lot of fun, kinda wish I saved it for Christmas.
The game is done really well with a choice between live music stations which you play along to and play with others to beat the score, or concerts. The concerts are real video/footage which has been edited, it's done really well and is shot from your prospective, it's really quite immersive.
Lots of songs and the ablitiy to obtain more (i believe for free if continue to play the game and earn coins) makes it unlikely to quickly become stale, like the other GHs.
For £36 with two guitars, it's a bargain.