Hi there!
When I needed to sort out my M1 Visa, I had the same reply from the US embassy in London (a nice 4 week wait) - so, I went to Lisbon, Portugal and had the appointment and visa issued in the same day!
The Consular chappy asked me why I had come to Portugal to get it sorted, and I simply said, I dont want to wait 4 weeks doing it through the embassy in London!
So, if you are desperate and can afford the expence of a plane ticket, go elsewhere!
Good luck!