BTL disaster? Not necassrily.
With the tightening of the credit market people, esp first time buyers, are going to find themselvers stuck in the private rented sector for a lot longer than they planned, this will swell the demand for private sector rented accomodation and keep rents bouyant.
There are also a number of people who sold up at the top of the market and are now in the rented sector waiting for the market to bottom out before buying again.
I think that the only place that will see a real price and rents depreciation is the SE of England where prices/rents were artificially high in any case. Up here in Scotland we still have above ave GDP growth, c8-10% house price growth and private rents are growing nicely