Let's test the criminality idea. Fraud in the UK is defined (via the Fraud Act 2006) as gain to oneself or loss to another by dishonest deception. We can work through the various activities of Jason Arday, and see if they qualify.
Plagiarism in PhD: This is straightforward in terms of deception; Jason Arday presented the work of another as his own, which is objectively an act of deception. It is probably dishonest; in a courtroom, one would apply the Ivey test, which would need to show that Arday knew that plagiarism was wrong, which would rely on what he was taught in his studies at university, but possibly not much of a challenge. However, a fraud needs a gain or loss, which is a financial consequence of an action. Merely plagiarising the work of others as part of a PhD would fail this test, so this activity would not be considered a fraud (still absolutely disgraceful behaviour, though).
Representing oneself as having a PhD: Once Arday was awarded his PhD, his use of this in seeking employment would not be a fraud offence; although he might have gained it via deception, his PhD aware is an objective fact, so there is no deception. A person might reasonably believe that an individual with a PhD has gained it through honest research, though I think it would be incredibly challenging to prosecute on this basis.
Gaining employment through deception: When Jason Arday obtained employment at the University of Cambridge, he had a CV which appears to have contained information which was untrue. This is likely to have been supplemented by statements during the employment process which were also untrue. Lying about one's achievements in a job application is deceptive (pretty much without question) and dishonest. The dishonesty aspect, moreover, is an objective point as, if one has not been employed in certain roles, this should not be used to obtain employment. Gaining employment through deception also fulfils the loss/gain aspect, as one gains a salary as a result. There is a considerable amount of precedent for fraud prosecutions for against individuals who have gained employment by deception. It isn't normally worthwhile for an employer to pursue criminal charges against an employee who acts in this way, but it is not unknown. There would be a strong case for a fraud prosecution against Arday here.
Random lying: We can be pretty certain that Arday didn't raise the amount of money he claimed for charity, but he gained nothing out of it (other than a bit of status), so unlikely to be something that could lead to a prosecution.