I've heard it rumoured a couple of times that a UK operator (aside from Flybe) is aiming to acquire 10 x DHC8-400s. I'm just putting 2 & 2 together here, so as always DYOR. However, there's obviously a few ex-SAS ones available.
In the circumstances it would be daft to replace the F50 with a lower capacity jet as Delta Wun-Wun states.