Hi!
I think this is a very good domain name.

Would be relatively easy to develop it. Something like an online directory of businesses. If I were you, would contact the businesses via a nicely written e-mail announcing the launch of SW1.biz.
You can set a price for each listing or list for free. Work on promotion of website, SEO.
How many unique visitors do you currently have?
Have you defined a traffic generation strategy for SW1.biz?
Do you currently generate any revenue from the Sedo domain parking service?
I see that it is not currently indexed and ranked in Google and other major search engines. If you have "negative" answers to the above three questions, then your domain name is currently appraised to low $XX.
If you develop the site, try to frequently add unique and quality content and apply Seach Engine Optimization (SEO) techniques. Then you are going to increase your visitors and thus your revenue (could be from contextual ads on SW1.biz). Your domain name could then be appraised to a high price - depends on how is the overall performance of your website.
Dim