IMO, Cv's are rediculously long. Resumes are usually only 1 or maybe 2 pages.
I think you have to be careful about assuming CVs are longer. It is going to come down to the employer, the position and your CV/resume writing skills (fluff is bad at any length). My office, which is almost entirely degree educated professionals, has a very strong preference for short CVs.
For example, we use a very strict one page limit for graduate positions. When we are sorting through 100+ CVs for 1 position, people who are materially longer than 1 page, particularly if they also have stupid formatting, will be eliminated almost instantly.
Listing things on a CV which are not relevant to the position you are applying for shows that you either don't understand the position or made very little effecting in applying for the position. If instructions or guidance are given on what the employer wants in regards to CVs or cover letters, the instructions can be a simple test to see if you can follow basic instruction.
This may be slightly off topic, but I have found that British universities are worse at preparing their students to apply for jobs. Maybe it is just where I went to university, but anyone who spent 10 minutes in the career services office at that uni could create better CVs than what most British students produce.