I don’t think “Pixie” or “Wee Burney” are at all derogatory, QM. I cannot, incidentally, claim credit for their invention. That honour goes to a well known journalist. But they both describe the physical appearance of the two politicians (provided, that is, you know where “Wee Burney” originates from).
I think, perhaps, “Lord Snooty” would be appropriate for Mr Cameron. He certainly bears a passing resemblance to the well known Beano character, though I’m not quite sure whether any of his “pals” fit the bill. I’m not really sure about Mr Farage. Of course he has not had the opportunity to break any promises as the others mentioned have.
Incidentally I do find the comparison between Lord Snooty breaking his pledges and Pixie and Burney breaking theirs is not quite valid. Lord Snooty, of course, has broken political and manifesto type pledges which almost all politicians are prone to do all the time. The undertakings the other two made were more personal. They led people to believe that they would be more than willing to accept a family of Syrian refugees into their homes. They have had plenty of opportunity to do just that as quite a number of Syrians have arrived under the government’s scheme. I’m sure they could have used their contacts to acquire some of them in order to fulfil their pledges but it seems they’ve been otherwise occupied. Personally I strongly believe we may never see their promises met. But I could be wrong.