I just bought a Steyr M9A1 from Wanstalls last week.
Fantastic service, prompt delivery.
As you've probably figured out, it's damn near impossible to find a Steyr to shoot before you've bought it - I bought mine based on specs and reviews alone and so far I am very happy with my purchase.
As others have said, magazines, accessories and parts will be hard to come by, but all can be procured over the internet with a little patience.
It's the best fitting grip I've ever felt on a pistol, the low bore axis really reduces muzzle flip and I love the (apparently controversial) trap sights.
IMHO you'll not find a better, cooler looking pistol for the money, and you will be the only one at the range who has one. Why buy what everyone else has?