With Sandisk CF cards they generally have the speed printed on them as an example
45 mb/s. the fastest being 90mb/s.
Ok why go for a reasonably fast card? When doing continuous shooting the transfer rate from camera to card can "stall" with a slow card until it can catch up with the camera, Therefore the camera has to wait for the card to catch up.
There is nothing worse than having to wait before you can continue with the camera using this setting, Murphy's Law states during the "stall" period you will miss the best shot of the sequence.
I prefer the Scandisk Extreme 1V 4gig or 8gig with a 45mb/s transfer rate as the minimum to prevent the above happening.
As regards to real Sandisk CF cards on thing to look for is on the edge where it says "Made in China" it should be preceeded with a serial number. Fake Sandisk cards often don't have this serial number, its just one quick easy check but don't use this as a hard and fast rule but worth noting.
Anna there is a shop called 7dayshop and I have made several purchases from them and they are based in the Channel Isles and can recommend, not to be confused with your 7daymemoryshop.
Quote " Anyhow, in Currys it had a poster in the wall advertising memory cards and as a guide it said for DSLRs you need 16 - 32 GB as it needs the speed." unquote.
This has absolutely nothing to do with speed on a DSLR camera, its just the amount of memory the card can hold and you definately don't need 16-32 gb card for a DSLR (only if you have a DSLR camera with movie mode) infact it can be a disadvantage. Should the card get damaged you have lost all the photos on it, and to download such a huge card onto computer would take ages. Another disadvantage is you might one day want to shoot pictures of wildlife and on another a friends wedding. With 2 or more smaller cards you can keep the subject seperate and work on each as and when you want in editing. Also if one card is damaged you havn't totally lost everything.
Realspeed