That would not happen in British law. Being an informant is not a guarantee of no prison term, though it might be seen as a mitigating circumstance, along with a plea of guilty and genuine emorse.
However, we must not get ahead of things.
Nobody has been charged with any offence, only arrested under caution and investigation.
Even if charged, a person is assumed innocent until and unless a Court of Law finds otherwise, on the grounds of clear evidence. Or of course pleads guilty: quite a lot of serious cases do end with the defendant realising he or she can no longer pretend innocence.
What IS being asked in the UK is who persuaded the government at the time, to appoint two people unfit to be trade envoy and ambassador to those roles. That's not suggesting any criminal offence, more likely incompetence and gullibility.
(Peter Mandelson was Britain's Trade Commissioner to the European Union, for Tony Blair's Labour government; after time as Blair's "Director of Communications".... whatever one of those does... then MP. Yet he was a career politician, who'd never run a business or worked as a civil-servant in any industry-relevant ministry in his life!
Nor had ex-Trade Envoy, Andrew Mountbatten-Windsor, though as a non-politician he had at least served in the real world, first in the Army then as an air-ambulance helicopter pilot. )
