Tesco Entertainment have loads of MP3 albums for £3 each:
Lady Gaga - The Fame Monster
Black Eyed Peas - The E.N.D.
Justin Bieber - My Worlds
Fyfe Dangerfield - Fly Yellow Moon
Mika - The Boy Who Knew Too Much
Pixie Lott - Turn It Up
...and many more
Stick two in your basket and use the code "MP3PROMO" to get £1 off a £5 or more spend, so two albums for £5! Quidco/Topcashback for 8% back too.