http://www.gamma498.plus.com/spondon%20engineering/^Their website.
I don't think there is a US dealer due to the fact they are a company who manufacture very little shelf stock, due to the cost of what they produce.
They aren't that expensive to be fair, and the quality is absolutely bang on point. Paying someone to strip a bike down and a give a good respray of the frame is probably about 2 thirds of the cost of a spondon frame, here in england.
The factory is about a 10 minute ride from my house and although the frames are scarce due to the fact replacing a frame is a big deal to most and its not cheap to obtain, I have seen several, and 2 fully road worthy 1200 bandits (one owned by suzuki bandit accesory specialists also in derbyshire, england).
At first I thought they'd had the frame polished and/or some work done to it. When i got closer I noticed the size of the tubing and some slight differences to the stock frame and fell in love.. that was my introduction to Spondon frames.
If you read about spondon's main aim in their early days they wanted to reduce weight and improve rigidity/handling of racing bikes. Not all the frames they produce today give masses of difference over stock due to the nature of todays sports bike technology etc, but with a bandit frame I think its safe to say you will notice the difference. I did when I was allowed to ride a friends for 10 minutes several months ago.
I think the other point would be, you would be one of incredibly few in the US with a spondon frame, if not the only person! Is price balanced by exclusivity..?
-Dave.