I wouldn't bet on it.
Brexit is something they have to figure out themselves. If the British Establishment wants to stop it, that's something they'll have to do at home. It's certainly not up to Donald Trump, who'll be busy with a lot of other stuff.
Faking a story like this would be a putting a lot of effort into something that won't have much of a pay-off and could really blow up in the perpetrators' faces. There are enough unhinged ex-intelligence agents in the world that this doesn't have to be anything more than some nut's private project.
Plus, I'd have thought Britain's Establishment would be a lot smarter than this (but I could be giving them too much credit).
FWIW, I think the Brits, or at least their uniparty, has something to hide.
I’m not sure if I believe there any U.K. Intelligence was truly involved. I think they are trying to make the story appear more believable as to how our CIA and Some media outlets fell for this ridiculous story. They are covering their ass big time.