Here's Dearlove on Brexit: https://briefingsforbrexit.com/jeremy-corbyn-and-national-se... ; he's retired, which allows him to speak on the subject.

The security services are supposed to be both secret and impartial, which makes it difficult to directly find out what they want, but campaigning against ECHR has been a common theme of Home Secretaries for years and Brexit is a necessary precondition for leaving ECHR.

And of course, what people wanted from Brexit and what they're going to get are two almost completely unrelated things.