I don´t think anyone seriously disputes that there will be a sell off of BTL properties or that the UK housing market still has some way to drop. What concerns me is the headline grabbing quote “Prices will drop by 55%”. It was in fact this that you chose to highlight in your post.
As I live in NL I have no financial interest in the UK property market. I really couldn´t care less what happens to prices there. I just get a bit ticked off by poor journalism which this IMO is.