As a British citizen with direct experience of two such cases, I would argue (with some degree of authority) that what's wrong with your argument is interpretation of what you've read (and the posters above too)
In the UK civil courts, both sides must prove the veracity of their arguments. Thus the plaintiff must show that the respondent's utterances were defamatory, and the respondent must must prove the veracity of his defence, by showing them to be truthful, justified or whatever defence he has chosen to employ. If you can prove the statement is true you will not be found to be guilty of defamation. The difference between the allowable and the absolute defence of truth in the UK & US courts respectively is merely this; in the US truth is an absolute defence and the justice systems explicitly forbids the court from finding in favour of the plaintiff, in the UK it is an allowable defence and historical precedence guides the court that in such cases the plaintiff cannot claim slander if the utterances were truthful.
Civil actions are not about proof as criminal cases are, they're more about putting forward a convincing argument.
Journalistic freedom is highly prized in the UK, and, though journalists' employers may run scared of litigation on occasion, it's very rare for such actions to be successful, and those which are are more often than not overturned at appeal.
The cases discussed here are viewed entirely differently (and rightly so) from the tabloid rumour-mongering which abounds in our newspaper industry