Unported Creative Commons licences are now on the third version (e.g. http://creativecommons.org/licenses/by/3.0/legalcode), and have improved quite significantly (the early ones were essentially US law licences, with some of the references to US law omitted).
As to which licence to choose, if the target audience for use of the licensed materials is the UK, the England & Wales version of the Creative Commons licences have jurisdiction-specific legal definitions and references. If appropriate, the Scottish versions could also be used. If there is a wider target audience than the UK, then use of the third generation unported licences might be the best. The definitions are a bit wordier than the UK national versions, and won’t dovetail quite as well with national legislation, but that’s the downside of an international audience in many jurisdictions. A compromise might be to offer UK-based users the benefit of their jurisdiction-specific licence, and anyone outwith the UK can use on the basis of the unported licence. The downside of this is the complexity of two different (though closely related) licensing regimes.