No, is the short answer. A feature of English law is that inertia is not normally criminal.You can watch a man drowning and not begin to save him or fetch help (unlike in France). If you see a crime you don't have to tell anyone. If you have evidence then you don't have to divulge it.(There are special rules for terrorism offences though)
It's only when you do something positive , some act, that is intended to pervert the course of justice or you obstruct the police in the execution of their duties or you knowingly assist an offender by , say, removing evidence, that you commit an offence.Refusing to answer questions under oath is not perjury.Positively telling lies though, is another matter (as, in some cases, is saying the stock answer 'I don't remember', though many a perjurer has believed so)
As to section 5 of the Criminal Law Act 1967, the first good news is that, in any case, it requires the consent of the Director of Public Prosecutions to institute proceedings and his department won't be bothered unless it's a really extreme case. The second good news is that 'consideration' must mean true consideration passing from the person who has committed the original offence, or some other person, to the defendant . It would not be 'consideration' passing to the defendant if he thought, correctly, that it would be safer or wiser not to say anything or to be an informer.Likewise if he stayed quiet in return for not being shot or suffering other punishment or persuasion, that forbearance by the gangster would not be true consideration passing to the defendant (apart from any question of duress in such a case)