I have used Sandisk CF cards within all of my Canon DSLR's for years and they have never let me down. £29.99 seems like a bargain for a fast reliable 8GB CF card. You can get lesser branded cards cheaper, but the Pro's all use Sandisk for a reason.
SanDisk Extreme III Compact Flash 8GB
Read Speed: 204x (30MB Per/Sec)
Write Speed: 204x (30MB Per/Sec)
Warranty: 10 Year
High Durability & Reliability
Includes Travel Case