Before buying I did a bit more research on my chosen recording. It was selected as the best recording of Beethoven 5 by Radio 3's CD Review in October 2007 and also by the website, classicalcdguide.com
At £6.02, Amazon offered a real bargain. It's important to get the right edition (catalogue number: DG 447 400 2). Slightly confused at first by there being two versions: one dated 1995 in standard CD format and another dated 2011 in SACD format. Super Audio CD sounds good but a quick google search suggested it wouldn't be possible to tell the difference, so at over £17 the SACD version didn't offer good value.